Gout and Pseudogout 

Updated: Mar 13, 2019
Author: Bruce M Rothschild, MD; Chief Editor: Herbert S Diamond, MD 

Overview

Practice Essentials

Gout and pseudogout are the 2 most common crystal-induced arthropathies. Gout (see the image below) is caused by monosodium urate monohydrate crystals; pseudogout is caused by calcium pyrophosphate crystals and is more accurately termed calcium pyrophosphate disease.

Gout. Acute podagra due to gout in elderly man. Gout. Acute podagra due to gout in elderly man.

Signs and symptoms

Symptoms of gout or pseudogout include the following:

  • Podagra (initial joint manifestation in 50% of gout cases and eventually involved in 90%; also observed in patients with pseudogout and other conditions)

  • Arthritis in other sites – In gout, the instep, ankle, wrist, finger joints, and knee; in pseudogout, large joints (eg, the knee, wrist, elbow, or ankle)

  • Monoarticular involvement most commonly, though polyarticular acute flares are not rare, and many different joints may be involved simultaneously or in rapid succession

  • In gout, attacks that begin abruptly and typically reach maximum intensity within 8-12 hours; in pseudogout, attacks resembling those of acute gout or a more insidious onset that occurs over several days

  • Without treatment, symptom patterns that change over time; attacks can become more polyarticular, involve more proximal and upper-extremity joints, occur more often, and last longer

  • In some cases, eventual development of chronic polyarticular arthritis that can resemble rheumatoid arthritis

Physical findings may include the following:

  • Involvement of a single (most common) or multiple joints

  • Signs of inflammation – Swelling, warmth, erythema (sometimes resembling cellulitis), and tenderness

  • Fever (also consider infectious arthritis)

  • Migratory polyarthritis (rare)

  • Posterior interosseous nerve syndrome (rare)

  • Tophi in soft tissues (helix of the ear, fingers, toes, prepatellar bursa, olecranon)

  • Eye involvement – Tophi, crystal-containing conjunctival nodules, band keratopathy, blurred vision, anterior uveitis (rare), scleritis

Complications of gout include the following:

  • Severe degenerative arthritis

  • Secondary infections

  • Urate or uric acid nephropathy

  • Increased susceptibility to infection

  • Urate nephropathy

  • Renal stones

  • Nerve or spinal cord impingement

  • Fractures in joints with tophaceous gout

See Presentation for more detail.

Diagnosis

Studies that may be helpful include the following:

  • Joint aspiration and synovial fluid analysis

  • Serum uric acid measurement (though hyperuricemia is not diagnostic of gout)

  • 24-hour urinary uric acid evaluation

  • Blood studies (including white blood cells [WBCs, triglyceride, high-density lipoprotein, glucose, and renal and liver function tests)

Plain radiographs may show findings consistent with gout. Erosions with overhanging edges are generally considered pathognomonic for gout (though also found in other diseases). Characteristics of erosions typical of gout include the following:

  • Maintenance of the joint space

  • Absence of periarticular osteopenia

  • Location outside the joint capsule

  • Sclerotic (cookie-cutter, punched-out) borders

  • Asymmetric distribution among the joints, with a strong predilection for distal joints, especially in the lower extremities

Ultrasonographic findings in established gout include the following:

  • A “double-contour” sign, consisting of a hyperechoic, irregular line of MSU crystals on the surface of articular cartilage overlying an adjacent hyperechoic bony contour

  • “Wet clumps of sugar,” representing tophaceous material, described as hyperechoic and hypoechoic heterogeneous material with an anechoic rim

  • Bony erosions adjacent to tophaceous deposits

Other imaging modalities that may be considered include the following:

  • Computed tomography (CT) – Complementary to plain radiography for recognizing erosions in gout

  • Magnetic resonance imaging (MRI) – MRI with gadolinium is recommended when tendon sheath involvement must be evaluated and when osteomyelitis is in the differential diagnosis

See Workup for more detail.

Management

Gout is managed in the following 3 stages:

  • Treating the acute attack

  • Providing prophylaxis to prevent acute flares

  • Lowering excess stores of urate to prevent flares of gouty arthritis and to prevent tissue deposition of urate crystals

Acute treatment of proven crystal-induced arthritis is directed at relief of the pain and inflammation. Agents used in this setting include the following:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs), such as indomethacin

  • Corticosteroids

  • Colchicine (now less commonly used for acute gout than it once was)

  • Adrenocorticotropic hormone (ACTH)

  • Combinations of drugs (colchicine plus NSAIDs, oral corticosteroids plus colchicine, intra-articular steroids plus colchicine or NSAIDs)

Therapy to control the underlying hyperuricemia generally is contraindicated until the acute attack is controlled (unless kidneys are at risk because of an unusually heavy uric acid load).

Long-term management of gout is focused on lowering uric acid levels. Agents used include the following:

  • Allopurinol

  • Febuxostat

  • Probenecid

Because these agents change serum and tissue uric acid levels, they may precipitate acute attacks of gout. This undesired effect may be reduced by prophylaxis with the following:

  • Colchicine or low-dose NSAIDs

  • Low-dose prednisone (if patients cannot take colchicine or NSAIDs)

Other therapeutic agents that may be considered include the following:

  • Uricase and pegloticase

  • Vitamin C

  • Anakinra

  • Fenofibrate

  • Lesinurad/allopurinol

Nonpharmacologic measures that may be warranted are as follows:

  • Avoidance or restricted consumption of high-purine foods

  • Avoidance of excess ingestion of alcoholic drinks, particularly beer

  • Avoidance of sodas and other beverages or foods sweetened with high-fructose corn syrup

  • Limited use of naturally sweet fruit juices, table sugar, and sweetened beverages and desserts, as well as table salt

  • Maintenance of a high level of hydration with water (≥8 glasses of liquids daily)

  • A low-cholesterol, low-fat diet, if such a diet is otherwise appropriate for the patient

  • Weight reduction in patients who are obese

See Treatment and Medication for more detail.

Background

Gout and pseudogout are the two most common crystal-induced arthropathies. Gout is caused by monosodium urate monohydrate crystals; pseudogout is caused by calcium pyrophosphate (CPP) crystals and is more accurately termed calcium pyrophosphate disease (CPPD). (See Pathophysiology and Etiology.) Gout is one of the oldest diseases in the medical literature,[1, 2] known since the time of the ancient Greeks. Pseudogout, which may be clinically indistinguishable from gout, was recognized as a distinct disease entity in 1962.

Crystal deposition can be asymptomatic, but gout and CPPD can develop into debilitating illnesses marked by recurrent episodes of pain and joint inflammation that result from the formation of crystals within the joint space and deposition of crystals in soft tissue.[3, 4, 5] If untreated, these disorders can lead to joint destruction and, in the case of uric acid crystals, renal damage.

Elevated serum uric acid levels are the principal risk factor for developing gout. lIn study that compared 993 patients with asymptomatic hyperuricemia and 4,241 normouricemic patients, the odds ratio (OR) for developing gout was 32 times higher in the hyperuricemic group than in the normouricemic group. The risk was most striking in men with severe hyperuricemia, in whom the OR for developing gout was 624.8.[6]

Although gout is associated with hyperuricemia, gout attacks are triggered not by a particular level of uric acid but typically by acute changes in the level of uric acid. All individuals with gout have hyperuricemia; however, hyperuricemia is also found in patients taking diuretics and even in those taking niacin or low doses of aspirin.

Gout may be either primary or secondary (see Etiology). Primary gout is related to underexcretion or overproduction of uric acid, often associated with a mix of dietary excesses or alcohol overuse and metabolic syndrome. Secondary gout is related to medications or conditions that cause hyperuricemia, such as the following[7] :

  • Myeloproliferative diseases or their treatment
  • Therapeutic regimens that produce hyperuricemia
  • Renal failure
  • Renal tubular disorders
  • Lead poisoning
  • Hyperproliferative skin disorders
  • Enzymatic defects (eg, deficient hypoxanthine-guanine phosphoribosyl transferase, glycogen storage diseases)

Gout is definitively diagnosed on the basis of demonstration of urate crystals in aspirated synovial fluid, in the absence of another etiology for arthritis. Classic radiographic findings are highly suggestive (see Workup).

Advances in early diagnosis and the availability of definitive treatment have significantly improved the prognosis of gout, as evidenced by the declining incidence of disabling chronic tophaceous gout. However, tophaceous gout may still develop because of misdiagnosis, poor management, medication intolerances, or poor patient adherence.

Gout is managed in the following 3 stages:

  • Treating the acute attack
  • Providing prophylaxis to prevent acute flares
  • Lowering excess stores of urate

Treatment of gout is important to relieve pain; to prevent disease progression; and to prevent deposition of urate crystals in the renal medulla or uric acid crystals in the renal collecting system, which may produce kidney stones or urate nephropathy.[8] (See Treatment.)

Management of pseudogout also involves treatment of the acute attack and prophylaxis. Treatment of the acute phase of pseudogout follows the same approaches as are used in gout, and colchicine is effective for prophylaxis. In contrast with gout, however, no specific therapeutic regimen exists to treat the underlying cause of CPP crystal deposition in pseudogout, except in cases associated with disorders such as hemochromatosis or hyperparathyroidism. (See Treatment.)

Pathophysiology

Gout can be considered a disorder of metabolism that allows uric acid or urate to accumulate in blood and tissues. When tissues become supersaturated, the urate salts precipitate, forming crystals. In addition, the crystals also are less soluble under acid conditions and at low temperatures, such as occur in cool, peripheral joints (eg, the metatarsophalangeal joint of the big toe).

Urate initially precipitates in the form of needlelike crystals. The light-retarding (phase-shifting) characteristics of urate crystals allow them to be recognized by polarizing microscopy (see the image below).

Gout. Needles of urate crystals seen on polarizing Gout. Needles of urate crystals seen on polarizing microscopy.

Many conditions and drugs have been associated with an increase in plasma (and subsequent synovial) urate levels, particularly metabolic syndrome.[9] A genetic predisposition for hyperuricemia exists; except in rare genetic disorders, however, the development of gout in hyperuricemic individuals appears to be mediated by environmental factors.[10, 11, 12]

The CPP crystals that produce pseudogout comprise a combination of inorganic pyrophosphate and calcium. The inorganic pyrophosphate is produced in large part by ectonucleotide phosphodiesterase pyrophosphatase (ENPP1), a catalytic enzyme found in chondrocytes of cartilage, and the pyrophosphate is exported potently by the membrane transporter ANKH.

A genetic predisposition exists for pseudogout. However, aging, some metabolic diseases (eg, hyperparathyroidism, hemochromatosis, and hypomagnesemia), and any process that leads to osteoarthritis also can be associated with subsequent CPP crystal deposition and pseudogout.

The presence of urate crystals in the soft tissues and synovial tissues is a prerequisite for a gouty attack. However, these crystals can also be found in synovial fluid or on the cartilage surface in the absence of joint inflammation.

A gout attack may be triggered either by release of crystals (eg, from partial dissolution of a microtophus caused by changing serum urate levels) or by precipitation of crystals in a supersaturated microenvironment (eg, release of urate as a consequence of cellular damage). In either situation, it is believed, naked urate crystals then interact with intracellular and surface receptors of local dendritic cells and macrophages, triggering a danger signal to activate the innate immune system.[13]

This interaction may be enhanced by immunoglobulin G (IgG) binding.[14, 15] Triggering of these receptors, including Toll-like receptors, followed by intracellular signaling by the NLRP3 inflammasome, results in the release of interleukin (IL)-1β, which in turn initiates a cascade of proinflammatory cytokines, including IL-6, IL-8, neutrophil chemotactic factors, and tumor necrosis factor (TNF)-α.[16, 17] Neutrophil phagocytosis leads to another burst of inflammatory mediator production.

Chatfield et al reported that the interaction of urate crystals with lysosomes results in the formation of web-like chromatin structures known as neutrophil extracellular traps (NETs) and subsequent cell death (NETosis), via a mechanism independent of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The urate crystal–induced NETs are enriched for actin and are resistant to degradation by serum and DNase; they coat the crystals with DNA, which then persist in tissues as gouty tophi.​[18]

Subsidence of an acute gout attack results from multiple mechanisms, including the clearance of damaged neutrophils, change in the properties of urate crystals, and the production of anti-inflammatory cytokines such as IL-1 receptor antagonist (IL-1RA), IL-10, and transforming growth factor (TGF)-β.[15, 19, 20, 21]

Etiology

Gout develops in the setting of excessive stores of uric acid in the form of monosodium urate. Uric acid is an end-stage by-product of purine metabolism. Humans remove uric acid primarily by renal excretion. When excretion is insufficient to maintain serum urate levels below the saturation level of 6.8 mg/dL, hyperuricemia may develop, and urate can crystallize and deposit in soft tissues.

About 90% of patients with gout develop excess urate stores because of an inability to excrete sufficient amounts of uric acid in the urine (underexcretion). Most of the remaining patients either overconsume purines or produce excessive amounts of uric acid endogenously (overproduction). A few have impaired intestinal elimination of uric acid.

In rare cases, overproduction of uric acid is the result of a genetic disorder, such as the following[22] :

  • Hypoxanthine-guanine phosphoribosyltransferase deficiency (Lesch-Nyhan syndrome)

  • Glucose-6-phosphatase deficiency (von Gierke disease)

  • Fructose 1-phosphate aldolase deficiency

  • Superactivity of phosphoribosyl pyrophosphate synthetase (PRPP)

Overproduction of uric acid may also occur in disorders that cause high cell turnover with release of purines that are present in high concentration in cell nuclei. These disorders include myeloproliferative and lymphoproliferative disorders, psoriasis, and hemolytic anemias.[23] Cell lysis from chemotherapy for malignancies, especially those of the hematopoietic or lymphatic systems, can raise uric acid levels, as can excessive exercise and obesity.

Causes of secondary gout due to underexcretion of uric acid include renal insufficiency, lead nephropathy (saturnine gout), starvation or dehydration, certain drugs, and chronic abuse of ethanol (especially beer and hard liquor). These disorders should be identified and corrected, if possible.[9]

Certain comorbid conditions are associated with a higher incidence of gout, including the following[24, 25] :

  • Hypertension
  • Diabetes mellitus
  • Renal insufficiency
  • Hypertriglyceridemia
  • Hypercholesterolemia
  • Obesity
  • Anemia

Foods that are rich in purines include anchovies, sardines, sweetbreads, kidney, liver, and meat extracts. Consumption of fructose-rich foods and beverages (eg, those sweetened with high-fructose corn syrup) is associated with an increased risk of gout in both men and women.[26, 27]

Genetics

The heritability of serum urate levels is estimated at 63%.[28] Genome-wide association studies (GWAS) have identified several candidate loci associated with chronically elevated serum urate concentrations and gout.[29, 30, 31, 32]

In particular, 3 genes are noted to have a strong association with hyperuricemia. The locus with the strongest evidence of association is the glucose transporter 9 (GLUT9) gene, commonly referred to as the solute carrier 2A9 (SLC2A9), the product of which alters the renal excretion of uric acid. Some of the variants are associated with a protective effect, whereas others convey a higher risk of gout.[33]

The urate transporter 1 (URAT1) gene is involved with the urate-organic anion exchanger. Several mutations in this gene have been associated with gout.

Polymorphisms in the ABCG2 gene, which is located on chromosome 4 and codes for an intestinal urate transporter, are strongly associated with high serum uric acid concentrations and gout. Elevation of uric acid levels is greater in men than in women with the minor allele of rs2231142 in ABCG2.[29, 31]

Although genetic factors have been strongly associated with hyperuricemia, environmental and other state-of-health factors are responsible for the majority of the gout burden in developed countries.[33, 34] A study of 514 male twin pairs did show a strong concordance in hyperuricemia among monozygotic (MZ) twins (53%) as compared with dizygotic (DZ) twins (24%), but it did not show a significant difference between MZ and DZ twins with regard to the lifetime prevalence of gout.[12]

Causes of gout flares

Individual gout flares are often triggered by acute increases or decreases in urate levels that may lead to the production, exposure, or shedding of crystals. Changes in urate levels can result from acute alcohol ingestion, acute overindulgence in foods high in purines, rapid weight loss, dehydration, or trauma.

Similarly, flares can be precipitated by additions of or changes in dosage of medications that raise or lower uric acid levels. Medications that increase uric acid levels via effects on renal tubular transport include the following[35, 36] :

  • Loop and thiazide diuretics
  • Niacin
  • Low-dose aspirin
  • Cyclosporine [37]
  • Pembrolizumab [38]  

​Agents that lower levels of uric acid include the following:

  • Radiocontrast dyes
  • Xanthine oxidase inhibitors (eg, allopurinol, febuxostat)
  • Uricosurics (eg, probenecid).

Pseudogout

Although the pathophysiology, clinical presentation, and acute-phase treatment of gout and pseudogout are very similar, the underlying causes of the 2 diseases are very different. Many cases of pseudogout in elderly people are idiopathic, but pseudogout has also been associated with trauma and with many different metabolic abnormalities, the most common of which are hyperparathyroidism and hemochromatosis.

Several drugs have been implicated as possibly responsible for induction of CPPD.[36, 39]  These include loop diuretics and proton pump inhibitors, both of which are associated with hypomagnesemia, and bisphosphonates. However, the role of these drugs in CPPD is controversial; they may even be protective. Anecdotal evidence links hyaluronic acid and granulocyte colony-stimulating factor as risk factors. Pseudogout attacks have been reportedly induced by etidronate disodium therapy and angiography.[40, 41]

Pseudogout has been recognized as having an underlying genetic component; however, comorbid conditions (such as osteoarthritis) and environmental factors are thought to play a much stronger role.[42] Some disorders that can lead to secondary pseudogout, such as hemochromatosis, do have a clear genetic cause. These patients should be properly evaluated and counseled.

Epidemiology

United States statistics

Gout affects 8.3 million people in the United States; prevalence among adults is estimated to be 3.9%, on the basis of data from the 2007-2008 National Health and Nutrition Examination Survey (NHANES).[43] Prevalence is approximately 20% in patients with a family history of gout. It is estimated that more than 2 million people in the United States take medication to decrease serum uric acid levels.

Gout has become increasingly common in the United States as the population has grown older and heavier.[44] From 1990 to 1999, the incidence rose 40%.[45] Estimates for the number of US adults with self-reported gout in the previous year rose from 2.1 million in 1995 to 3 million in 2008.[11] In 2008, gout accounted for 174,823 emergency department (ED) visits in the US, or approximately 0.2% of all ED visits.[46]

The frequency of pseudogout varies with age. The annual incidence of acute attacks of arthritic pain and swelling is about 1.3 per 1000 adults, but nearly 50% of adults develop radiographic changes typical of CPPD by age 80 years.

Attacks of gout have been noted to occur more frequently in the spring and less frequently in the winter. The reason for this is unknown.

International statistics

Gout has a worldwide distribution. The prevalence varies widely from country to country. Regional differences may reflect environmental, dietary, and genetic influences.[47]

In the United Kingdom from 2000 to 2007, the incidence of gout was 2.68 per 1000 person-years—4.42 in men and 1.32 in women, and increasing with advancing age.[48] In Italy, the prevalence of gout rose from 6.7 per 1000 population in 2005 to 9.1 per 1000 population in 2009, increasing with age and 4 times higher in men.[49] In the Maori people of New Zealand, studies from the 1970s found that 0.3% of men and 4.3% of women were affected.[50, 51]

Sex- and age-related demographics

Gout has a male predominance.[27, 52] The estimated prevalence of gout is 5.9% in men and 2% in women.[43] This difference is largely a consequence of age at onset; estrogenic hormones have a mild uricosuric effect, and gout is therefore unusual in premenopausal women. For pseudogout, the male-to-female ratio is approximately 50:50.

The predominant age range of gout is 30-60 years. Usually, uric acid levels are elevated for 10-20 years before the onset of gout. In men, uric acid levels rise at puberty, and the peak age of onset of gout in men is in the fourth to sixth decade of life. However, onset may occur in men in their early 20s who have a genetic predisposition and lifestyle risk factors.[53] In women, uric acid levels rise at menopause, and peak age of onset is in the sixth to eighth decade of life.

The rate of gout is almost 5 times higher in persons aged 70-79 years than in those younger than 50 years.[54] The higher prevalence of gout in elderly persons may also reflect an increased prevalence of metabolic syndrome, high rates of diuretic treatment for hypertension and chronic heart failure, and the use of low-dose aspirin.[55]

Earlier onset of gout occurs in patients with renal insufficiency or a genetic abnormality of purine metabolism (eg, hypoxanthine-guanine phosphoribosyltransferase deficiency or phosphoribosylpyrophosphate synthetase superactivity). Cyclosporine A can cause an accelerated form of gout, even in premenopausal women, that can present after only a few years of hyperuricemia, particularly if the patient is also receiving diuretics.

Race-related demographics

Gout has an increased prevalence in some populations but is rare in others. For example, the frequency of gout is higher in populations such as the Chamorros and Maori and in the Blackfoot and Pima tribes. Many Maori and other Polynesian women have a genetic defect in renal urate handling that places them at risk for hyperuricemia and gout.[56] However, racial differences may at least in part reflect differences in diet, which has a large influence on the clinical expression of gout.

In the United States, the incidence of gout is 3.11 per 1000 person-years in African Americans and 1.82 per 1000 person-years in whites; the excess risk can be partly explained by a higher frequency of incident hypertension.[57] In contrast, clinically recognized gout is extremely rare among blacks living in Africa.[58]

Prognosis

Gout is associated with considerable morbidity, with acute episodes often causing incapacitation. However, gout that is treated early and properly carries an excellent prognosis if patient adherence to treatment is good.

With early treatment, gout should be totally controlled. If attacks recur, successful uric acid adjustment (requiring lifelong use of urate-lowering medication) usually suppresses further activity. During the first 6-24 months of urate-lowering therapy, acute attacks of gout often occur more frequently.[59, 60]

Chronic injury to intra-articular cartilage leaves the joints more susceptible to subsequent joint infections. Draining tophi can become secondarily infected. Untreated chronic tophaceous gout can lead to severe joint destruction and, rarely, renal impairment. Deposition of monosodium urate crystals in the kidney can result in inflammation and fibrosis, leading to reduced renal function or chronic nephropathy.[61] Rarely, gout can produce spinal cord impingement when deposition in tissues produces a local mass.

Acute attacks of pseudogout usually resolve within 10 days. Prognosis for resolutions of acute attacks is excellent. Some patients experience progressive joint damage with functional limitation. CPPD also can cause chronic arthritis that can resemble osteoarthritis or rheumatoid arthritis. Results of a study by Hubert et al suggest that osteoarthritis of the ankle can be a complication of CPPD.[62]

Hyperuricemia and gout are associated with an increased overall likelihood of mortality. Whether this is directly attributable to hyperuricemia or gout or to gout-associated diseases (eg, insulin resistance, type 2 diabetes mellitus, abdominal obesity, hypercholesterolemia, or hypertension) has been much debated.[63, 64, 65]

Although no evidence has shown that gout or hyperuricemia causes any of these disorders, elevated urate levels have been shown to correlate with elevated blood pressure in adolescents.[66] Among middle-aged men, hyperuricemia is a significant independent risk factor for death from cardiovascular disease.[67] A meta-analysis found an independent association between gout and cardiovascular mortality as well as all-cause mortality.[65]

In a 2010 study, Kuo et al demonstrated that gout, but not hyperuricemia, is associated with higher risk of death from all causes and cardiovascular diseases. Analysis of 1383 deaths among 61,527 Taiwanese subjects showed in individuals with gout compared with those who had normal uric acid levels, the hazard ratio (HR) of all-cause mortality was 1.46 and the adjusted HR of cardiovascular mortality was 1.97. Among individuals with hyperuricemia, the HR of all-cause mortality was 1.07 and the adjusted HR of cardiovascular mortality was 1.08.[68]

An analysis of nationwide data on more than 200,000 English patients indicates that individuals with gout are at increased risk for both heart attack and stroke. The rate ratio for myocardial infarction in patients with gout was 1.82. Rate ratios for stroke were 1.71 for all stroke, 1.68 for ischemic stroke, 1.69 for hemorrhagic stroke, and 2.00 for stroke of unspecified type. Risks were elevated in both men and women and were higher in the younger age groups.[69, 70]

Risk for vascular disease is increased in patients with gout, particularly women, according to a retrospective cohort study from the United Kingdom that included 8386 patients with gout and 39,766 matched controls. Multivariate analysis showed that women with gout had a 25% increased risk for any vascular event compared with women without gout (hazard ratio [HR], 1.25) and increased risks for any coronary heart disease (HR, 1.25) and peripheral vascular disease (HR, 1.89).[71, 72]

Men with gout, compared with those without gout, had a small but significantly increased risk for any vascular event (hazard ratio [HR], 1.06) and an increased risk for any coronary heart disease (HR, 1.08) and peripheral vascular disease (HR, 1.18). Unlike women, men with gout were not at greater risk for angina, transient ischemic attack, or stroke.[71, 72]

In contrast, urate-lowering therapy (ULT) in patients with gout has been linked to reduced risk for both cardiovascular (CV) mortality and all-cause mortality. A prospective case-matched cohort study by Chen et al of Taiwanese patients followed for 6.5 years found that patients with gout who received ULT with either allopurinol or benzbromarone had a lower risk of CV disease (HR 0.29) and all-cause mortality (HR 0.47) relative to patients with gout not treated with ULT.[73]

Similarly, Solomon and colleagues reported a reduced risk of a CV event in patients with gout who take colchicine. Their analysis of data from an electronic medical record database on 1002 gout patients, with a median follow-up of 16.5 months, found that the incidence rates of myocardial infarction, stroke, or transient ischemic attack were 35.6 per 1000 person-years for colchicine users and 81.8 for non-users. Adjusted risk of a CV event was 49% lower with colchicine use (HR 0.51) and all-cause mortality was 73% lower (HR 0.55).[74]

 

Patient Education

Patients with severe hyperuricemia should avoid foods with high purine content. Moderation in food and alcohol consumption is advised. Early recognition of acute gout attacks is critical, in that intervention with medication is much more effective earlier in the attack.

For patient education information, see the Arthritis Center, as well as Gout. Online information and pamphlets on gout are also available from the Arthritis Foundation.

What is gout? Gout is an inflammatory disease where uric acid precipitates into crystals that deposit in various joints around the body, causing pain and inflammation. This video describes the pathophysiology, causes, symptoms, and treatment of gout.
 

Presentation

History

The spontaneous onset of excruciating pain, edema, and inflammation in the metatarsal-phalangeal joint of the great toe (podagra; see the image below) is highly suggestive of acute crystal-induced arthritis. Podagra is the initial joint manifestation in 50% of gout cases; eventually, it is involved in 90% of cases. Podagra is not synonymous with gout, however: it may also be observed in patients with pseudogout, sarcoidosis, gonococcal arthritis, psoriatic arthritis, and reactive arthritis.

Gout. Acute podagra due to gout in elderly man. Gout. Acute podagra due to gout in elderly man.

Other than the great toe, the most common sites of gouty arthritis are the instep, ankle, wrist, finger joints, and knee. In early gout, only 1 or 2 joints are usually involved. Consider the diagnosis in any patient with acute monoarticular arthritis of any peripheral joint except the glenohumeral joint of the shoulder.

The most common sites of pseudogout arthritis are large joints, such as the knee, wrist, elbow, or ankle. Case reports have documented carpal tunnel syndrome as an initial presentation of pseudogout. Case reports of calcium pyrophosphate (CPP) crystals forming masses in the spinal ligamentum flavum have been documented.[75] These have led to both single-level and multilevel myelopathy.

Although crystal-induced arthritis is most commonly monoarticular, polyarticular acute flares are not rare, and many different joints may be involved simultaneously or in rapid succession. Multiple joints in the same limb often are involved, as when inflammation begins in the great toe and then progresses to involve the midfoot and ankle.

Gout attacks begin abruptly and typically reach maximum intensity within 8-12 hours. Affected joints are red, hot, and exquisitely tender; even a bed sheet on the swollen joint is uncomfortable. The onset of symptoms in pseudogout can resemble acute gout or be more insidious and may occur over several days.

Untreated, the first attacks resolve spontaneously in less than 2 weeks. A history of intermittent inflammatory arthritis, in which the joints return to normal between attacks, is typical of crystalline disorders and is characteristic of gouty arthritis early in its course.

Gout initially presents as polyarticular arthritis in 10% of patients. Elderly women, particularly women with renal insufficiency who are taking a thiazide diuretic, can develop polyarticular arthritis as the first manifestation of gout. These attacks may occur in coexisting Heberden and Bouchard nodes. Such patients may also develop tophi more quickly, occasionally without prior episodes of acute gouty arthritis.[76, 77, 78]

The pattern of symptoms in untreated gout changes over time. The attacks can become more polyarticular. More proximal and upper-extremity joints become involved. Attacks tend to occur more frequently and last longer.

Eventually, patients may develop chronic polyarticular arthritis, sometimes nearly symmetrical, that can resemble rheumatoid arthritis. Indeed, chronic polyarticular arthritis that began as an intermittent arthritis should prompt consideration of a crystalline disorder in the differential diagnosis.

Acute flares of gout can result from situations that lead to increased levels of serum uric acid, such as the consumption of beer or liquor, overconsumption of foods with high purine content, trauma, dehydration, or the use of medications that elevate levels of uric acid. Acute flares of gout also can result from situations that lead to decreased levels of serum uric acid, such as the use of radiocontrast dye or medications that lower the levels of uric acid, including allopurinol and uricosurics. (See Overview/Etiology.)

Patients with gout have as much as 1000 times more uric acid in the body as unaffected individuals do and are almost twice (1.97 times) as likely to develop renal stones as healthy individuals are[79] ; therefore, they may have a history of renal colic and hematuria. Indeed, renal stones may precede the onset of gout in 14% of affected patients. Whereas 52% of these patients may have stones composed entirely of uric acid, 20% may develop calcium oxalate or sometimes calcium phosphate stones.[80]

Because gout is frequently present in patients with the metabolic syndrome (eg, insulin resistance or diabetes, hypertension, hypertriglyceridemia, and low levels of high-density lipoproteins) and because the presence of these associated disorders can lead to coronary artery disease, these problems should be sought and treated in patients diagnosed with gout.

It is important to ask about a history of peptic ulcer disease, renal disease, or other conditions that may complicate the use of the medications used to treat gout.

Fever, chills, and malaise do not distinguish cellulitis or septic arthritis from crystal-induced arthritis, because all 3 illnesses can produce these signs and symptoms. A careful history may uncover risk factors for cellulitis or septic arthritis, such as possible exposure to gonorrhea, a recent puncture wound over the joint, or systemic signs of disseminated infection.

Physical Examination

Patients experiencing an acute attack of gout or pseudogout most often present with involvement of a single joint. However, all joints must be examined to determine whether the patient’s arthritis is monoarticular or polyarticular. Involved joints have all the signs of inflammation: swelling, warmth, erythema, and tenderness.

The erythema over the joint may resemble cellulitis; the skin may desquamate as the attack subsides. The joint capsule becomes quickly swollen, resulting in a loss of range of motion of the involved joint.

Patients may be febrile during an acute gout attack, particularly if it is polyarticular. However, it is important to look for sites of infection that may have seeded the joint and caused an infectious arthritis resembling or coexisting with acute gouty arthritis.

Migratory polyarthritis is a rare presentation. Polyarticular gout commonly involves the small joints of the fingers and toes, as well as the knees. An inflammatory synovial effusion may be present. Uncommonly, acute gout may present as carpal tunnel syndrome.

Posterior interosseous nerve syndrome is a rare compression neuropathy that manifests as inability to extend the fingers actively. The syndrome has been reported in a patient with elbow swelling from an attack of pseudogout; in this case, treatment with intra-articular steroids led to resolution of the nerve palsy.[81]

Patients with established gout may have chronic arthritis. Affected joints evidence tenderness and swelling, with or without redness, warmth, or joint damage.

Tophi

Although gout typically causes joint inflammation, it can also cause inflammation in other synovial-based structures, such as bursae and tendons. Tophi are collections of urate crystals in the soft tissues. They tend to develop after about a decade in untreated patients who develop chronic gouty arthritis. Tophi may develop earlier in older women, particularly those receiving diuretics.[76, 77, 78]

Tophi are classically located along the helix of the ear, but they can be found in multiple locations, including the fingers, the toes, the prepatellar bursa, and along the olecranon, where they can resemble rheumatoid nodules (see the images below). Rarely, a creamy discharge may be present.[82, 83] The finding of an apparent rheumatoid nodule in a patient with a negative rheumatoid factor assay or a history of drainage from a nodule should prompt consideration of gout in the differential diagnosis.[84]

Gout. Tophaceous deposits in ear. Gout. Tophaceous deposits in ear.
Gout. Tophaceous deposits on elbow. Gout. Tophaceous deposits on elbow.
Gout. Chronic tophaceous gout in untreated patient Gout. Chronic tophaceous gout in untreated patient with end-stage renal disease.

Eye involvement

The folklore surrounding gout has also involved the eye, and before the 20th century, a myriad of common and unusual ocular symptoms were falsely ascribed to gout. Medical science has since documented eye involvement as a rare but definite aspect of gout. All manifestations of gout in the eye are secondary to deposition of urate crystals within the ocular tissue.[85, 86]

Tophi have been described in the eyelids.[87, 88, 89] Conjunctival nodules containing needlelike crystals have been described within the interpalpebral areas, sometimes associated with a mild marginal keratitis. Band keratopathy with refractile, yellow crystals in the deep corneal epithelial cells and at the level of the Bowman membrane are not uncommon.[90]

Blurring of vision from the corneal haze or a foreign body sensation due to epithelial breakdown may occur. Gout rarely can be associated with anterior uveitis; Duke-Elder mentions this as a cause of hemorrhagic iritis in his classic Text Book of Ophthalmology. Scleritis and tendinitis have also been described. Besides the cornea, the iris, anterior chamber, lens, and sclera have been found to harbor urate crystals; on postmortem examination, urate crystals have also been found in tarsal cartilage and in the tendons of extraocular muscles.[85, 86]

Complications

Complications of gout include the following:

  • Severe degenerative arthritis
  • Secondary infections
  • Urate or uric acid nephropathy
  • Increased susceptibility to infection
  • Urate nephropathy
  • Renal stones
  • Nerve or spinal cord impingement [91, 92]
  • Fractures in joints with tophaceous gout [93]

 Calcification of the atlas transverse ligament has been reported in 44-70% of individuals with calcium pyrophosphate disease (CPPD), with frequency increasing with age.[94]  A significantly elevated rate of non-union of type II and III odontoid fractures has been reported in patients with CPPD (90.3%, versus 32% in controls).[95]

 

DDx

Diagnostic Considerations

The cause of new-onset acute monoarticular arthritis cannot be reliably determined from the history and physical examination alone. Septic arthritis, gout, and pseudogout can present in very similar ways.

Nevertheless, certain clinical presentations are so characteristic of gout that attempts have been made to diagnose or exclude gout without joint aspiration. Janssens et al developed a diagnostic rule for this purpose, which included the following diagnostic criteria[96] :

  • Male sex
  • Previous arthritis attack
  • Onset within 1 day
  • Joint redness
  • First metatarsophalangeal joint involvement
  • Hypertension or 1 or more cardiovascular diseases
  • A serum uric acid level higher than 5.88 mg/dL

In a study of this rule in 328 patients, the positive predictive value of gout diagnosis by family physicians was 0.64; the negative predictive value was 0.87.[96]

Nevertheless, the criterion standards for the diagnosis of gout remain the following:

  • Demonstration of intracellular monosodium urate crystals
  • Exclusion of infection or other crystal types in the synovial fluid from the inflamed joint

Patients who present with acute inflammatory arthritis need to undergo arthrocentesis to exclude septic arthritis, even if their serum uric acid level is elevated. Nongonococcal infectious arthritis carries a 10% fatality rate and therefore must be excluded.

Other problems to be considered in the differential diagnosis of gout and pseudogout include the following:

  • Acute sarcoidosis
  • Amyloidosis
  • Bursitis
  • Calcific periarthritis
  • Chondrocalcinosis
  • Congenital fructose intolerance
  • Conjunctival calcinosis
  • Hyperparathyroidism
  • Hypoxanthine-guanine phosphoribosyltransferase deficiency (Lesch-Nyhan syndrome)
  • Malignant soft tissue tumors
  • Milk-alkali syndrome
  • Multicentric reticulohistiocytosis
  • Paronychia
  • Pigmented villonodular synovitis
  • Phosphoribosylpyrophosphate synthetase superactivity
  • Psoriatic arthropathy
  • Reactive arthritis
  • Renal osteodystrophy
  • Spondyloarthropathy
  • Rheumatoid arthritis
  • Tenosynovitis
  • Trauma
  • Type IIA hyperlipoproteinemia

Differential Diagnoses

 

Workup

Approach Considerations

Arthrocentesis of the affected joint is mandatory for all patients with new-onset acute monoarthritis and is very strongly recommended for those with recurrent attacks whose diagnosis has never been proved by microscopic visualization of crystals. Tophi also may be aspirated for crystal analysis under polarizing microscopy.

A prior history of gout or pseudogout does not rule out the possibility of acute septic arthritis. In fact, the latter is more common in patients with a history of crystal-induced arthritis. Septic arthritis must be diagnosed and treated promptly, because irreversible damage can occur within 4-6 hours and the joint can be completely destroyed within 24-48 hours.

Send joint fluid for fluid analysis, including cell count and differential, Gram stain, culture and sensitivity, and microscopic analysis for crystals. If crystals are seen, their shape and appearance under polarized light are diagnostic.

In gout, crystals of monosodium urate (MSU) appear as needle-shaped intracellular and extracellular crystals. When examined with a polarizing filter and red compensator filter, they are yellow when aligned parallel to the slow axis of the red compensator but turn blue when aligned across the direction of polarization (ie, they exhibit negative birefringence). Negatively birefringent urate crystals are seen on polarizing examination in 85% of specimens.

Microscopic analysis in pseudogout shows calcium pyrophosphate (CPP) crystals, which appear shorter than MSU crystals and are often rhomboidal. Under a polarizing filter, CPP crystals change color depending upon their alignment relative to the direction of the red compensator. They are positively birefringent, appearing blue when aligned parallel with the slow axis of the compensator and yellow when perpendicular.

In crystal arthritis, the white blood cell (WBC) count in the synovial fluid is usually 10,000-70,000/µL. However, it may be as low as 1000/µL or as high as 100,000/µL.

Even in the presence of crystals in the joint fluid, blood cultures are indicated if any sign of systemic toxicity is present. Septic arthritis can occur in patients with active crystalline arthropathy.

Gouty attacks are not related to serum levels of uric acid. Thus, an elevated serum uric acid level does not prove the diagnosis of acute gout, though hyperuricemia is present in 95% of cases, and a normal level does not exclude the diagnosis. Renal uric acid excretion should be measured in high-risk patients, including those with renal calculi, a strong family history of gout, and a first attack before age 25 years.

Pseudogout attacks can be triggered by many metabolic abnormalities. Thus, patients who have an initial attack of arthritis with CPP crystals should have a workup that includes a chemistry screen; serum magnesium, calcium, and iron levels; and thyroid function tests.

The WBC count in peripheral blood is usually elevated, with a left shift during acute attacks. The erythrocyte sedimentation rate (ESR) usually is elevated during acute attacks.

Imaging studies of the affected joint or joints are indicated. Patients with new onset of acute gout usually have no radiographic abnormalities. In established disease, radiographs may reveal punched-out erosions or lytic areas with overhanging edges.

Magnetic resonance imaging (MRI) is capable of detecting crystal deposits but is not part of any routine evaluation for acute arthritis. MRI can be very useful in determining the extent of the disease and may help in the differential diagnosis.

Patients with pseudogout usually have degenerative joint changes evident on imaging studies. In addition, they may have calcifications in the soft tissues, tendons, or bursae.

Synovial Fluid Analysis

When a patient presents with acute inflammatory monoarticular arthritis, aspiration of the involved joint is critical to rule out an infectious arthritis and to attempt to confirm a diagnosis of gout or pseudogout on the basis of identification of crystals (see the image below). Minute quantities of fluid in the shaft or hub of the needle are sufficient for synovial fluid analysis.

Gout. Fluid obtained from tophaceous deposit in pa Gout. Fluid obtained from tophaceous deposit in patient with gout.

Urate crystals are shaped like needles or toothpicks with pointed ends (see the first image below). Under polarizing light microscopy, urate crystals are yellow when aligned parallel to the axis of the red compensator and blue when aligned across the direction of polarization (ie, they exhibit negative birefringence). Finding negatively birefringent urate crystals (see the second image below) firmly establishes the diagnosis of gouty arthritis.

Gout. Needles of urate crystals seen on polarizing Gout. Needles of urate crystals seen on polarizing microscopy.
Gout. Strongly negative birefringent, needle-shape Gout. Strongly negative birefringent, needle-shaped crystals diagnostic of gout obtained from acutely inflamed joint.

Pseudogout crystals (CPP) are rod-shaped with blunt ends and are positively birefringent. Thus, pseudogout crystals are blue when aligned parallel to the slow ray of the compensator and yellow when they are perpendicular.

Crystals must be distinguished from birefringent cartilaginous or other debris. Debris may have fuzzy borders and may be curved, whereas crystals have sharp borders and are straight. As alkalization reduces uric acid crystal solubility and the enzyme uricase can “dissolve” these crystals, reduction by addition of sodium hydroxide or uricase to suspected gout crystal can be helpful.

Corticosteroids injected into joints have a crystalline structure that can mimic either MSU or CPP crystals. They can be either positively or negatively birefringent.

The sensitivity of a synovial fluid analysis for crystals is 84%, with a specificity of 100%. If gout remains a clinical consideration after negative analysis findings, the procedure can be repeated in another joint or with a subsequent flare. Crystals may be absent very early in a flare.

Although the sensitivity of this test is inferior, aspiration of synovial fluid from previously inflamed joints that are not currently inflamed may reveal urate crystals. Such crystals are generally extracellular.

Synovial fluid should also be sent for cell count. During acute attacks, the synovial fluid is inflammatory, with a WBC count higher than 2000/µL (class II fluid) and possibly higher than 50,000/µL, with a predominance of polymorphonuclear neutrophils, though low WBC counts are occasionally found.

Synovial fluid glucose levels are usually normal, whereas they may be depressed in septic arthritis and occasionally in rheumatoid arthritis. Measurement of synovial fluid protein has no clinical value.

Crystalline arthritis and infectious arthritis can coexist. Indeed, infectious arthritis is more common in previously damaged joints, which may occur in patients with chronic gouty arthritis. Consequently, in patients with acute monoarticular arthritis, send synovial fluid for Gram stain and culture and sensitivity.

The pathologic specimens must be processed anhydrously. MSU is water-soluble and dissolves in formalin; therefore, only the ghosts of urate crystals may be seen if formalin is used. Absolute (100%) alcohol–fixed tissue is best for identification of urate crystals.

Once a diagnosis of gout is established by confirmation of crystals, repeat aspiration of joints with subsequent flares is not necessary unless infection is suggested or the flare does not respond appropriately to therapy for acute gout.

Serum Uric Acid

Measurement of serum uric acid is the most misused test in the diagnosis of gout. The presence of hyperuricemia in the absence of symptoms is not diagnostic of gout. In addition, as many as 15% of patients with symptoms from gout may have normal serum uric acid levels at the time of their attack. Thus, the diagnosis of gout can be missed if the joint is not aspirated. Remember that situations that decrease uric acid levels can trigger attacks of gout. In such cases, the patient’s medical records may reveal prior elevations of uric acid.

Approximately 25% of the population has a history of elevated serum uric acid, but only a minority of patients with hyperuricemia develop gout. Thus, an abnormally high serum uric acid level does not indicate or predict gout. As noted, gout is diagnosed by the presence of urate crystals in the synovial fluid or soft tissues. More important, some patients who present with a hot swollen joint and an elevated serum uric acid level in fact have infectious arthritis, which may be mismanaged if their synovial fluid is not examined.

Asymptomatic hyperuricemia generally should not be treated. However, patients with levels higher than 11 mg/dL and overexcretion of uric acid are at increased risk for renal stones and renal impairment; therefore, renal function should be monitored in these individuals.[34]

The level of serum uric acid does correlate with the risk for developing gout. The 5-year risk for developing gout is approximately 0.6% if the level is below 7.9 mg/dL, 1% if it is 8-8.9 mg/dL, and 22% if it is higher than 9 mg/dL.

Urinary Uric Acid

A 24-hour urinary uric acid evaluation is generally performed if uricosuric therapy is being considered. If patients excrete more than 800 mg of uric acid in 24 hours while eating a regular diet, they are overexcretors and thus overproducers of uric acid. These patients (approximately 10% of patients with gout) require allopurinol instead of probenecid to reduce uric acid levels. Furthermore, patients who excrete more than 1100 mg in 24 hours should undergo close renal function monitoring because of the risk of stones and urate nephropathy.

In patients in whom probenecid is contraindicated (eg, those with a history of renal stones or renal insufficiency), a 24-hour urine test of uric acid excretion need not be performed, because the patient clearly will need allopurinol.

Blood Studies

Blood studies may reveal abnormalities associated with gout or common comorbid conditions. In addition, abnormal results on renal function or liver function studies may affect the selection of therapy.

Obtaining an accurate measure of the patient’s renal function before deciding on therapy for gout is important. The glomerular filtration rate can be estimated by using formulas such as the Modification of Diet in Renal Disease (MDRD) Study equation or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Serum creatinine evaluation alone can underestimate renal dysfunction in elderly patients or in patients with low muscle mass.

The WBC count may be elevated in patients during the acute gouty attack, particularly if it is polyarticular. Hypertriglyceridemia and low levels of high-density lipoprotein (HDL) are associated with gout. Glucose measurement is useful because patients with gout are at increased risk for the development of diabetes mellitus.

Pseudogout attacks can be triggered by many metabolic abnormalities. Thus, patients who have an initial attack of arthritis with CPP crystals should have a workup that includes a chemistry screen; serum magnesium, calcium, iron and iron-binding levels; and thyroid function tests.

Radiography

Plain radiographs may show findings consistent with gout, but these findings are not diagnostic. Early in the disease, radiographs are often normal or show only soft-tissue swelling. Radiographic findings characteristic of gout, which generally do not appear within the first year of disease onset, consist of punched-out erosions or lytic areas with overhanging edges (see the image below). Haziness suggestive of tophi can be seen in late gout, and tophi may calcify.

Gout. Radiograph of erosions with overhanging edge Gout. Radiograph of erosions with overhanging edges.

Erosions with overhanging edges generally are considered pathognomonic for gout but also can be found in amyloidosis, multicentric reticulohistiocytosis, and type IIA hyperlipoproteinemia. Characteristics of erosions that are typical of gout but not of rheumatoid arthritis include the following:

  • Maintenance of the joint space[97, 98]

  • Absence of periarticular osteopenia

  • Location outside the joint capsule

Another characteristic of erosions typical of gout is sclerotic borders, sometimes called cookie-cutter or punched-out borders. In addition, erosions in gout may be distributed asymmetrically among the joints, with strong predilection for distal joints, especially in the lower extremities (see the images below).

Gout. Plain radiograph showing typical changes of Gout. Plain radiograph showing typical changes of gout in first metatarsophalangeal joint and fourth interphalangeal joint.
Gout. Plain radiograph showing chronic tophaceous Gout. Plain radiograph showing chronic tophaceous gouty arthritis in hands.

Ultrasonography

At the first attack, sites affected with gout may be anechoic on ultrasonography. Later, diffuse enhancement may be evident on the articular cartilage surface.[99] Chondrocalcinosis show up as a thin, hyperechoic band within hyaline cartilage and punctuated pattern on fibrocartilage.

Ultrasonographic findings in established gout include the following[100, 101, 102] :

  • A “double-contour” sign, consisting of a hyperechoic, irregular line of MSU crystals on the surface of articular cartilage overlying an adjacent hyperechoic bony contour

  • “Wet clumps of sugar,” representing tophaceous material, described as hyperechoic and hypoechoic heterogeneous material with an anechoic rim

  • Bony erosions adjacent to tophaceous deposits

The double contour sign is 85% sensitive and 80% specific for crystalline arthritis in general, with specificity for gout of 64% and for calcium pyrophosphate deposition disease of 52%.[103] The reliability of the double contour sign varies with the joint: femoral condyle sensitivity and specificity are 42% and 100%, respectively, compared with 62% and 98% for first metatarsals.[104]

Ultrasonography may demonstrate urate crystal deposition in tissues of asymptomatic patients with hyperuricemia. Pineda et al found double-contour signs in the first metatarsal-phalangeal joints of 25% of 50 asymptomatic patients with hyperuricemia but in none of 52 normouricemic subjects.[105]

Ultrasonography had higher sensitivity than radiography for detection of calcium pyrophosphate crystal deposition (CPPD) in a study by Ottaviani et al. In 51 patients, ultrasonography revealed hyperechoic spots in all 25 patients with CPPD (sensitivity 100%, specificity 92.3%), whereas radiography revealed CPPD in 16 of the 25 (sensitivity 64%, specificity 100%; P < 0.0001).[106]

In a study by Forien et al that included 32 patients with CPPD and 26 controls, the sensitivity of wrist ultrasonography for the diagnosis of CPPD was 94% while that of wrist radiography was 53.1%; the specificity of ultrasonography was 85%, versus 100% for radiography.[107] Ultrasonography revealed chondrocalcinosis in 35 joints with no radiographic evidence of chondrocalcinosis, and x-rays showed chondrocalcinosis in 3 joints without ultrasonographic chondrocalcinosis, thus indicating the complementary benefit of utilizing both techniques.

In a study by DeMiguel et al, ultrasonography identified urate crystal deposition in 11 of 26 patients who had asymptomatic hyperuricemia for 2-28 years (average, 6.2 years), affecting the knee in nine cases and the first metatarsal-phalangeal joint in six. These results document that asymptomatic gout may not be as innocuous as was once believed.[108]

Ultrasonography has good sensitivity and specificity for detecting tendon involvement, which occurs frequently in gout. In a controlled study by Ventura-Rios et al, which included 80 patients with gout, intra-tendinous tophi were found in tendon insertions at the distal patella, quadriceps, Achilles, and proximal patella.[109]

Computed Tomography

Plain radiography and computed tomography (CT) are complementary for recognizing erosions in gout.[110] Dual-energy CT, using a renal stone color-coding protocol, assesses chemical composition, labeling urate deposits in red.[111] In a case report, Ward et al describe the use of dual-energy CT to diagnose tumoral calcium pyrophosphate crystal deposition, differentiating it from gouty tophus or soft-tissue malignancy.[112]

In a study comparing CT imaging versus a history of urinary tract calculus for identification of nephrolithiasis in gout patients, 62% of the patients with CT-documented scans had no history of urolithiasis. In 383 male patients with primary gout, CT scanning confirmed nephrolithiasis in 103 (26.9%), whereas the history of urinary tract calculus was positive in only 65 (17%). The authors concluded that the prevalence of urolithiasis cannot be accurately determined on the basis of patients’ histories.[113]

Magnetic Resonance Imaging

MRI is not part of any routine evaluation for acute arthritis. MRI evidence of edema is minimal in gout, unless concomitant osteomyelitis is present.[114] However, MRI with gadolinium is recommended when tendon sheath involvement must be evaluated and when osteomyelitis is in the differential diagnosis. Large deposits of crystals may be seen in bursae or ligaments. MRI examination of erosions reveals tophi but no bone edema or synovitis.[115]

Tophi usually have low or intermediate signal intensity on T1-weighted spin echo images. Signal intensity also tends to be low on T2-weighted images. In the absence of inflammation, the tophi are sharply delineated. Presence of inflammation results in increased perilesional signal intensity. Tophi and the surrounding area of inflammation enhance with gadolinium.[116]

In a study of 10 cadaveric knees by Abreu et al, radiographic imaging and histologic analysis demonstrated widespread CPPD crystal deposition in four of the specimens (40%), while MRI demonstrated some calcifications only within the articular cartilage of the femoral condyles in three of those four specimens. In all four specimens, radiographs and histologic analysis had higher sensitivity than MRI.[117]

Histology

Chronic tophaceous gouty deposits frequently show large pale pink acellular areas, which represent dissolved urate crystals, surrounded by histiocytes and multinucleated giant cells (see the image below).

Gout. Hematoxylin and eosin (H&E) stain, low power Gout. Hematoxylin and eosin (H&E) stain, low power, showing abundant pale pink areas surrounded by histiocytes and multinucleated giant cells.

The crystals are water-soluble and thus are dissolved during routine tissue processing. If there are a large number of crystals, however, some may survive processing and appear as pale brown-gray refractile material (see the image below), or they may be seen on unstained sections. The urate crystals are easily seen on polarized light.

Gout. H&E stain, high power, showing that most ura Gout. H&E stain, high power, showing that most urate crystals have been dissolved but that some pale brown-gray crystals did survive processing.

Pseudogout also demonstrates pale pink areas that may be surrounded by histiocytes and multinucleated giant cells. On higher-power views, however, the crystals are purple and rhomboid and therefore can be distinguished from gout on routine histology (see the images below).

H&E stain, medium power, of pseudogout with pale p H&E stain, medium power, of pseudogout with pale pink fibrocartilage in upper portion and purple crystals of calcium pyrophosphate in lower portion.
Pseudogout. H&E stain, high power, under polarized Pseudogout. H&E stain, high power, under polarized light to highlight rhomboidal crystals.
Pseudogout. H&E stain, high power, of calcium pyro Pseudogout. H&E stain, high power, of calcium pyrophosphate crystals, demonstrating their rhomboidal structure.
 

Treatment

Approach Considerations

Gout is managed in the following 3 stages:

  • Treating the acute attack
  • Providing prophylaxis to prevent acute flares
  • Lowering excess stores of urate to prevent flares of gouty arthritis and to prevent tissue deposition of urate crystals

In 2012, the American College of Rheumatology (ACR) published guidelines on the treatment and prophylaxis of acute gouty arthritis and the management of hyperuricemia.[118, 119]  While those guidelines do describe treatment targets, more recent publications have focused more closely on the treat-to-target concept, although for the most part these recommendations are based on underlying principles and expert opinion rather than trial data.[120, 121, 122, 123]

As a general rule, asymptomatic hyperuricemia should not be treated, though ultrasonographic studies have demonstrated that urate crystal deposition into soft tissues occurs in a minority of patients with asymptomatic hyperuricemia.[105, 108] Patients with levels higher than 11 mg/dL who overexcrete uric acid are at risk for renal stones and renal impairment; therefore, renal function should be monitored in these individuals.[34]

Urate-lowering therapy appears to reduce the incidence of kidney damage in gout.[124] In a retrospective study of 16,186 patients with initial serum uric acid levels above 7 mg/dL, Levy and colleagues found that patients with gout who remained on urate-lowering therapy were less likely to develop kidney damage leading to chronic kidney disease than those who were untreated.[124] All patients were followed for 36 months from their first documented high serum uric acid level.

Patients who achieved a serum uric acid level below 6 mg/dL had a 37% improvement in renal outcomes (P< 0.0001).[124] The hazard ratio for kidney damage was 1.08 (95% confidence interval, 0.76–1.52) in patients who received urate-lowering therapy more than 80% of the time and was 1.27 (95% confidence interval, 1.05–1.55) in those who received urate-lowering therapy less than 80% of the time.

In a study of gout flares in patients newly started on urate-lowering therapy, Rashid et al found that 68% of these patients had one or more gout flares during the first 12 months of therapy.[125] Patients 65 years of age and older were more likely to have three or more flares. Other risk factors for gout flares included the following:

  • Male gender
  • Failure to attain serum uric acid goal
  • Presence of three or more comorbidities
  • Use of diuretics
  • No changes in initial urate-lowering therapy dose
  • Nonadherence to urate-lowering therapy

These findings echo those of other studies and emphasize the importance of providing close coverage, patient education, and prophylaxis against gout flares, especially during the first year of urate-lowering therapy.

Tophi should not be surgically removed unless they are in a critical location or drain chronically. Surgery may be indicated for tophaceous complications, including infection, joint deformity, compression (eg, cauda equina or spinal cord impingement), and intractable pain, as well as for ulcers related to tophaceous erosions. Delayed healing is noted in 50% of patients.

An international working group has developed treat-to-target recommendations for gout. In the absence of randomized trials comparing standard treatment with treat-to-target approaches in gout, the recommendations were based on indirect evidence and expert recommendations.[126, 127] The treatment targets are as follows:

  • Serum uric acid levels reduced below 6 mg/dL (5 mg/dL in patients with severe gout, such as tophi or frequent attacks) and maintained there
  • Tophi reduced in number or size
  • Pain reduction
  • Absence of attacks

Patients should have regular monitoring (eg, every 3-6 months) to assess whether targets are being met.

Treatment of the acute phase of pseudogout is identical to that of acute gout. In patients with idiopathic pseudogout, a deterrent regimen of colchicine may be used. If an underlying metabolic problem is responsible for pseudogout, the arthritis may be cured when the underlying problem is addressed.

Treatment of Acute Attacks

The temptation to treat patients without a proven diagnosis must be resisted. Septic arthritis may clinically resemble gout or pseudogout, and unrecognized septic arthritis can lead to loss of life or limb. Distinguishing septic arthritis from crystal-induced arthritis is not possible without an examination of joint fluid.

Acute treatment of proven crystal-induced arthritis is directed at relief of the pain and inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, colchicine, and adrenocorticotropic hormone (ACTH) are treatment options. The choice is based primarily on whether the patient has any concomitant health problems (eg, renal insufficiency or peptic ulcer disease). Colchicine, a classic treatment, is now rarely indicated.

When comorbid conditions limit the use of NSAIDs or colchicine, a preferred option may be an intra-articular steroid injection, particularly when a large, easily accessible joint is involved. Septic arthritis must be reasonably excluded.

Therapy to control the underlying hyperuricemia generally is contraindicated until the acute attack is controlled (unless kidneys are at risk because of an unusually heavy uric acid load). Starting therapy to control hyperuricemia during an acute attack may intensify and prolong the attack. If the patient has been on a consistent dosage of probenecid or allopurinol at the time of the acute attack, however, the drug should be continued at that dosage during the attack.

Furthermore, control of hyperuricemia generally is not pursued for a single attack. If attacks are recurrent or evidence of tophaceous or renal disease is present, therapy for control of hyperuricemia is indicated.[128, 129, 130]

Nonsteroidal anti-inflammatory drugs

NSAIDs are the drugs of choice in most patients with acute gout who do not have underlying health problems. Although indomethacin is the NSAID traditionally chosen for acute gout, most of the other NSAIDs can be used as well. Select an agent with a quick onset of action. Do not use aspirin, because it can alter uric acid levels and potentially prolong and intensify an acute attack. Low-dose aspirin alters uric acid levels, increasing the risk of gout attacks and requiring close uric acid monitoring when aspirin is added to a uric acid/gout treatment regimen.[131]

Cyclooxygenase-2 (COX-2) inhibitors have been used with success, but patients may require higher dosages than are typically used.[132]

Avoid NSAIDs in patients with a history of peptic ulcer disease or gastrointestinal (GI) bleeding, those with renal insufficiency or abnormal hepatic function, those taking warfarin (a selective COX-2 inhibitor can be used), and those in the intensive care unit (ICU) who are predisposed to gastritis. Limit NSAID use in elderly patients, because of the potential for adverse central nervous system (CNS) effects. Use NSAIDs cautiously in patients with diabetes and those who are receiving concomitant angiotensin-converting enzyme (ACE) inhibitors.

To control the acute attack, NSAIDs are prescribed at full dosage for 2-5 days. Once the acute attack is controlled. the dosage is reduced to approximately one half to one fourth of that amount. Taper the dosage over approximately 2 weeks. Gout symptoms should be absent for at least 2 days before the NSAID is discontinued.

Colchicine

Although colchicine was once the treatment of choice for acute gout, it is now less commonly used than NSAIDs because of its narrow therapeutic window and risk of toxicity.[133, 134] To be effective, colchicine therapy is ideally initiated within 36 hours of onset of the acute attack. When used for acute gout in classic hourly dosing regimens (no longer recommended), colchicine causes adverse GI effects, particularly diarrhea and vomiting, in 80% of patients.

Dosing recommendations for colchicine in the treatment of acute gout have undergone modifications as awareness of its toxicities has increased. Newer recommendations trend toward lowered daily and cumulative doses.[133, 135]

The regimen currently favored consists of 1.2 mg of colchicine, followed by 0.6 mg 1 hour later to initiate treatment of the early gout flare. In a multicenter, randomized, double-blind, placebo-controlled, parallel-group study, Terkaltaub et al found that this regimen yielded both maximum plasma concentration and early gout flare efficacy comparable with those of high-dose colchicine (4.8 mg total over 6 hours), with a safety profile indistinguishable from that of placebo.[136]

Data from 7 separate drug-to-drug interaction (DDI) studies suggests colchicine dose reductions of 33-66% for treatment of acute gout and 50-75% for prophylaxis when colchicine is given in combination with the extended-release calcium channel blockers verapamil and diltiazem or with the numerous P-gp and/or CYP3A4 inhibitors (eg, clarithromycin and cyclosporine); in addition, patients should avoid grapefruit juice. Dosages of colchicine did not have to be adjusted when the drug was used in combination with azithromycin.[137]

Colchicine should generally be avoided if the glomerular filtration rate (GFR) is lower than 10 mL/min, and the dose should be decreased by at least half if the GFR is lower than 50 mL/min. Colchicine should also be avoided in patients with hepatic dysfunction, biliary obstruction, or an inability to tolerate diarrhea.

A clinical response to colchicine is not pathognomonic for gout. Responses may also occur in patients with pseudogout, sarcoid arthropathy, psoriatic arthritis, or calcific tendonitis.

In February 2008, the US Food and Drug Administration (FDA) ruled that intravenous (IV) colchicine can no longer be produced or shipped in the United States, because of its toxicities. Consequently, IV colchicine is no longer advocated for the treatment of acute gout in the United States.[138]

Corticosteroids

Corticosteroids can be given to patients with gout who cannot use NSAIDs or colchicine. Steroids can be given orally, IV, intramuscularly (IM), or intra-articularly. Using parenteral corticosteroids confers no advantage unless the patient cannot take oral medications.

Prednisone can be given at a dose of approximately 40 mg for 1-3 days, which is then tapered over approximately 2 weeks (tapering more rapidly can result in a rebound flare). Monitor closely for corticosteroid effects. If treatment continues for more than 2 weeks, consider measures to prevent osteoporosis.

Intra-articular long-acting (depot) corticosteroids are particularly useful in patients with a monoarticular flare to help reduce the systemic effects of oral steroids. Ensuring that the joint is not infected before injecting intra-articular corticosteroids is particularly important.

An alternative to corticosteroid administration is to give ACTH (40 IU subcutaneously, with repeat dosing as needed) to induce production of corticosteroid by the patient’s own adrenal glands. Such a regimen does not depend on the patient for proper tapering of prednisone.

Combination therapy

If the patient does not have an adequate response to initial therapy with a single drug, ACR guidelines advises that adding a second appropriate agent is acceptable. Using combination therapy from the start is appropriate for an acute, severe gout attack, particularly if the attack involves multiple large joints or is polyarticular. Acceptable regimens include any of the following, in full or prophylactic doses as appropriate[119] :

  • Colchicine plus NSAIDs
  • Oral corticosteroids plus colchicine
  • Intra-articular steroids plus colchicine or NSAIDs

Treatment of Chronic Gout

When a patient experiences a first attack of gout, any medication regimens that may have contributed to the gout attack must be altered, and any predisposing medical conditions or habits must be addressed.[139] Patients should be instructed to go on a diet if obese, to stop drinking beer, and to avoid purine-rich foods.

In many cases, patients who have a first attack of gout should undergo therapy with agents that lower uric acid, given the high risk for further inflammatory attacks and the potential for destructive tophaceous deposition in the bone, synovium, and kidney, even without episodes of acute inflammation. If the first attack is not severe, however, some rheumatologists advocate waiting for a second attack before initiating such therapy; not all patients experience a second attack, and some patients may require convincing that they need life-long therapy.

The risk of a second attack of gout after the first attack is 62% after 1 year, 78% after 2 years, and 93% after 10 years. The decision to begin therapy depends partly on the baseline serum uric acid levels (> 9 mg/dL denotes a higher risk for recurrent gouty arthritis and tophi).

ACR guidelines recommend pharmacologic urate-lowering therapy for patients with gout who have 1 or more tophi on clinical examination or imaging study or have frequent attacks of acute gouty arthritis (≥2 attacks per year); once the target level has been achieved, uric acid should be monitored at 6-month intervals.[140] Less robust evidence supports pharmacologic therapy for patients with chronic kidney disease of stage 2 or worse or a past history of urolithiasis.[118]

Long-term management of gout is focused on lowering uric acid levels. The goal of therapy is to reduce serum uric acid levels to below 6 mg/dL, at minimum. In many cases, lowering uric acid levels to less than 5 mg/dL is necessary to improve the signs and symptoms of gout. ACR guidelines recommend that once palpable tophi and all acute and chronic gout symptoms have resolved, serum uric acid levels should be maintained below 6 mg/dL indefinitely.[118]

In contrast, Perez-Ruiz et al have proposed that once dissolution of existing urate crystals has been achieved, less stringent control may suffice to prevent formation of new crystals.[141] In their prospective cohort study of 211 patients from whom urate-lowering therapy was withdrawn either after 5 years if no tophus was present at baseline or 5 years after resolution of the last tophus, no patient who maintained an average serum urate level lower than 7 mg/dL developed a crystal-proven recurrence of gout.

Controversially, a 2016 guideline from the American College of Physicians (ACP) does not recommend the "treat to target" approach to controlling serum uric acid levels. The ACP concluded that evidence was insufficient to determine whether the benefits of escalating urate-lowering therapy to reach a serum urate target outweigh the harms associated with repeated monitoring and medication escalation.[142, 143]

Avoiding the use of medications that elevate uric acid in patients with gout is prudent. Thus, in patients with hypertension, other agents are preferable to a thiazide diuretic, provided that blood pressure can be managed easily with a single drug. Low-dose aspirin is also uricosuric. The angiotensin-receptor blocker (ARB) losartan should be considered, because it is uricosuric at 50 mg/day. However, medications that elevate uric acid can still be used, if required, by making appropriate adjustments of allopurinol or probenecid doses.

Urinary excretion amounting to less than 800 mg per 24-hour period on an unrestricted diet is considered underexcretion. Underexcreting patients are candidates for uricosuric therapy with probenecid. The dosage is increased at monthly intervals until the uric acid level is lowered to target. Urinary alkalization (eg, with potassium citrate) and ingestion of copious amounts of fluid are adjunctive recommendations.

In patients with gout who have renal disease, ACR guidelines recommend xanthine oxidase inhibitor therapy with either allopurinol or febuxostat as the first-line pharmacologic approach. Probenecid can be used in patients who have contraindications to or are intolerant of at least 1 of those first-line agents, or it may be combined with a xanthine oxidase inhibitor if the inhibitor does not lower uric acid sufficiently.[118] Probenecid could also be used for those patients who consider the risks of xanthine oxidase inhibitors to be too high.

The ACR advises, however, that monotherapy with probenecid is not a first-line choice in patients with a creatinine clearance of less than 50 mL/min.[118] In addition, drug interactions may occur with probenecid (see Medication).

Prophylaxis

Because allopurinol, febuxostat, and probenecid change serum and tissue uric acid levels, they may precipitate acute attacks of gout. To reduce this undesired effect, colchicine or low-dose NSAID treatment is provided for at least 6 months. In patients who cannot take colchicine or NSAIDs, low doses of prednisone can be considered. When used prophylactically, colchicine can reduce such flares by 85%.[144] Patients with gout may be able to abort an attack by taking a single colchicine tablet at the first twinge of an attack.

The standard dosage of colchicine for prophylaxis is 0.6 mg twice daily, but lower dosages have also been suggested. Significant dosage reduction is critical for patients who are also taking calcium channel blockers (eg, verapamil or diltiazem) and any of the large number of P-gp or CYP3A4 inhibitors (eg, clarithromycin or cyclosporine). In patients with renal insufficiency, the dosing frequency may have to be decreased to once daily or every other day.

Adverse GI effects are uncommon with this dosage, occurring in only 4% of patients. This stands in contrast to the 80% risk of adverse GI effects with the classic hourly colchicine regimen for the treatment of acute gout.

Even in prophylactic doses, however, long-term use of colchicine can lead to marrow toxicity and to neuromyopathy, with elevated levels of creatine kinase and resulting muscle weakness. Colchicine-induced neuromyopathy is a particular risk in patients with renal insufficiency.[145]

If the patient develops a gout flare after beginning therapy with a uric acid–lowering agent, the agent should not be discontinued, because discontinuance will only cause another flux in the uric acid level, which may prolong and intensify the attack.

Allopurinol

Allopurinol blocks xanthine oxidase and thus reduces the generation of uric acid. Approximately 3-10% of patients taking allopurinol develop symptoms of intolerance, such as dyspepsia, headache, diarrhea, or pruritic maculopapular rash.

Less frequently (1% of cases), patients taking allopurinol can develop severe allopurinol hypersensitivity syndrome, which carries a mortality of 20-30%.[146] Features of this syndrome include fever, toxic epidermal necrolysis, bone marrow suppression, eosinophilia, leukocytosis, renal failure, hepatic failure, and vasculitis. Corticosteroids are often used to treat severe allopurinol hypersensitivity syndrome.

Severe allopurinol hypersensitivity syndrome is more likely to occur in patients with renal insufficiency, those who are taking a thiazide diuretic, and those started on allopurinol at a dosage of 300 mg/day.[147] In addition, strong associations have been found between severe allopurinol hypersensitivity reactions and carriage of the HLA–B*5801 allele.[148]

ACR guidelines recommend considering screening for HLA–B*5801 carriage, using a polymerase chain reaction–based test, in selected high-risk patients before starting allopurinol. Patients at particularly high risk are known to include those of Han Chinese or Thai descent; Koreans are also at risk, if they have stage 3 or worse chronic kidney disease.[118] It is unclear whether such precautions are necessary with a 100-mg starting dose of allopurinol. Additionally, availability of this test may be an issue.

Severe allopurinol hypersensitivity syndrome may present as Stevens-Johnson syndrome or as drug rash with eosinophilia and systemic symptoms (DRESS) syndrome. DRESS syndrome affects the liver, kidney, and skin. It is a delayed-hypersensitivity response occurring 6-8 weeks after initiation of allopurinol. The underlying mechanism is thought to be a cell-mediated immune reaction to allopurinol and its metabolites. Although the frequency is only is 0.4%, the rate of organ failure and death is high. Treatment is with IV N- acetylcysteine and steroids.

Allopurinol should immediately be discontinued in patients who develop pruritus or a rash consistent with allopurinol hypersensitivity.

In most patients, start allopurinol at 100 mg/day (50 mg/day in patients with renal insufficiency). Stamp et al have proposed that the risk of allopurinol hypersensitivity may be reduced by starting allopurinol at a dose of 1.5 mg per unit of estimated GFR.[149]

Adjust the dosage upward every 2-5 weeks according to the uric acid level until the goal of a uric acid level of 6 mg/dL or less is achieved. Once the target uric acid level has been achieved and maintained for 6 months, discontinue colchicine prophylaxis, unless the patient has 1 or more tophi on clinical exam.

Previously, adjusting the allopurinol maintenance dosage to the creatinine clearance rate was recommended for patients with renal insufficiency. However, Vázquez-Mellado et al found no increase in the prevalence of adverse reactions to allopurinol in patients who were started at an adjusted dosage but subsequently had their dosage raised to meet therapeutic targets.[150]

ACR guidelines advise that the dosage of allopurinol can be raised above 300 mg/day, even in patients with renal impairment, provided that the patient receives adequate education and monitoring for drug toxicity (including measurement of transaminase levels). The maximum dosage of allopurinol approved by the US Food and Drug Administration (FDA) is 800 mg/day,[118] but the maximum dosage should be lower in patients with chronic kidney disease.

Beware of drug interactions. For example, allopurinol prolongs the half-life of azathioprine and 6-mercaptopurine. It enhances the bone marrow toxicity of cyclophosphamide. Patients taking concomitant ampicillin are at an increased risk of rash.

Allopurinol can be used in combination with probenecid. However, note that probenecid increases the excretion of allopurinol.

In a retrospective 24-month study of gout patients who had been prescribed allopurinol, Riedel et al found that only 18% of them filled all their prescriptions throughout the entire follow-up period and thus were presumably compliant; 10.4% filled only a single prescription.[151] In contrast, Rees et al reported that when patients receiving urate-lowering therapy were given a predominantly nurse-delivered intervention that included education and individualized lifestyle advice, 92% achieved target serum uric acid levels at 1 year.[152]

Febuxostat

Febuxostat, a nonpurine selective inhibitor of xanthine oxidase, is a potential alternative to allopurinol in patients with gout.[153, 154, 155] Febuxostat is administered orally and is metabolized mainly in the liver. In contrast, allopurinol and its metabolites are excreted primarily by the kidney. Therefore, febuxostat can be used in patients with renal impairment with no dosage adjustment.[156] It is more expensive than allopurinol.

The CONFIRMS trial demonstrated the efficacy and safety of febuxostat in lowering hyperuricemia. By 6 months, the primary endpoint—a serum uric acid level of less than 6.0 mg/dL—was achieved in 45% of subjects on febuxostat 40 mg/day, 67% on febuxostat 80 mg/day, and 42% on allopurinol. In subjects with renal impairment, the primary endpoint was achieved in 50% of subjects on febuxostat 40 mg/day, 72% on febuxostat 80 mg/day, and 42% on allopurinol. Adverse event rates were low and similar in all groups.[157]

In patients aged 65 years or older, the primary endpoint was achieved in 62% on febuxostat 40 mg/day, 82% on febuxostat 80 mg/day, and 47% on allopurinol. These figures remained essentially unchanged in subjects with mild-to-moderate renal impairment.[158]

In African-American subjects, the primary endpoint was reached in 47% on febuxostat 40 mg/day, 68% on febuxostat 80 mg/day, and 43% on allopurinol. Similar rates were seen in subjects with renal impairment.[159] Adverse event rates in both subgroups were comparable with those in the overall trial.

The efficacy and safety of febuxostat in women was demonstrated in the CONFIRMS trial and in 2 other trials comparing febuxostat and allopurinol: FACT (Febuxostat Versus Allopurinol Controlled Trial) and APEX (Allopurinol- and Placebo-Controlled, Efficacy Study of Febuxostat). Achievement of a uric acid level below 6.0 mg/dL rose with increasing daily doses of febuxostat doses, from 54.3% in patients receiving 40 mg to 100% in those receiving 240 mg, compared with 45.9% with allopurinol. Results were similar in subjects with renal impairment.[160]

Stepwise introduction of febuxostat—10 mg/day for 4 weeks, then 20 mg/day for 4 weeks, then 40 mg/day—was found to reduce gout flares, in randomized open-label comparative study by Yamanaka et al.[161] Although flares still occurred, their frequency was reduced even in absence of colchicine coverage, so this approach may also be of benefit for individuals with significant contraindications to colchicine or NSAIDs.

White et al reported that all-cause mortality and cardiovascular mortality were higher with febuxostat than with allopurinol (hazard ratio [HR] for death from any cause, 1.22; HR for cardiovascular death, 1.34).[162] In February 2019 the US Food and Drug Administration (FDA) added a black box warning regarding increased risk of death with febuxostat compared with allopurinol. The FDA also limited the approval of febuxostat to use in cases of allopurinol therapeutic failure or intolerance.[163]

Lesinurad

Lesinurad (Zurampic) is the first selective uric acid reabsorption inhibitor (SURI) approved by the FDA. It acts by inhibiting the urate transporter, URAT1, which is responsible for the majority of the renal reabsorption of uric acid. It also inhibits organic anion transporter 4 (OAT4), a uric acid transporter associated with diuretic-induced hyperuricemia.

Lesinurad must be coadministered with a xanthine oxidase inhibitor and is for hyperuricemia associated with gout in patients who have not achieved target serum uric acid levels with a xanthine oxidase inhibitor alone. Monotherapy or higher than recommended doses are associated with an increased serum creatinine. Renal function should be assessed before initiating therapy and periodically thereafter. More frequent monitoring is required for an estimated CrCl < 60 mL/min. Do not initiate therapy if CrCl is < 45 mL/min and discontinue if CrCl decreases persistently to < 45 mL/min.

Approval was based on 3 randomized, placebo-controlled studies in combination with a xanthine oxidase inhibitor involving 1,537 participants for up to 12 months. Participants treated with lesinurad plus allopurinol or febuxostat experienced reduced serum uric acid levels compared with placebo.[164]

In a randomized double-blind study of 227 patients with an inadequate response to allopurinol, the addition of lesinurad to the prestudy allopurinol dose resulted in significant mean reductions of serum uric acid levels from baseline. Levels decreased 16%, 22%, and 30% with lesurinad doses of 200, 400, and 600 mg, respectively. In comparison, patients receiving placebo demonstrated a mean 3% increase in serum uric acid levels (P < 0.0001, all doses vs placebo). Similar results were observed in patients with mild or moderate renal insufficiency.[165]

Uricase

Nonrecombinant urate-oxidase (uricase) is used in Europe to prevent severe hyperuricemia induced by chemotherapy in patients with malignancies, as well as in selected patients with treatment-refractory gout. Short-term use of such agents in patients with severe tophaceous gout could debulk the total-body urate load, allowing maintenance with probenecid or allopurinol.

In 2009, the FDA approved recombinant uricase (rasburicase) for the prevention of tumor lysis syndrome. However, it is highly immunogenic and may cause anaphylaxis.[166]

In 2010, a polyethylene-glycol–conjugated uricase (pegloticase) was approved by the FDA for gout. Pegloticase, which enzymatically catalyzes the oxidation of uric acid to allantoin, is an IV biologic agent to be considered when adjustment of contributing medications (eg, diuretics) and treatment with allopurinol, febuxostat, and uricosuric agents are insufficient to achieve appropriate reduction of serum uric acid levels.[118] The European Medicines Agency (EMA) has approved use of pegloticase in Europe.[167]

Adverse effects of pegloticase include anaphylaxis, infusion reactions, gout flares, and exacerbation of congestive heart failure. At present, substantial expense compromises its cost-effectiveness as an initial approach.[168] The ACR guidelines do not recommend pegloticase as a first-line approach.

Other therapeutic options

Benzbromarone is an effective uricosuric agent available on a restricted basis only outside the United States. However, it has been withdrawn because it causes fulminant hepatotoxicity.

Vitamin C, with its uricosuric effect, may reduce the serum concentration of uric acid. In one study, 500 mg/day for 2 months reduced uric acid by a mean of 0.5 mg/dL in patients without gout.[169] However, gout patients appear to be less responsive to such a low dose of ascorbate. Vitamin C treatment should be avoided in patients with nephrolithiasis, urate nephropathy, or cystinuria.

Kobylecki et al reported that each 10 µmol/L higher plasma vitamin C level was associated with a 2.3 µmol/L lower plasma urate level. However, carriage of the SLC23A1 genetic variant, which causes lifelong high plasma vitamin C levels, was not associated with plasma urate levels or with risk of hyperuricemia.[170]

In an open-label pilot study of 10 patients with refractory acute gout treated with the interleukin (IL)-1 antagonist anakinra, pain was substantially reduced in all patients within 2 days, without side effects. Clinical signs of inflammation had disappeared in 9 of 10 patients by day 3 of treatment.[171]

The lipid-lowering drug fenofibrate, a fibric acid derivative, lowers serum uric acid levels while reducing very-low-density lipoprotein (VLDL), total cholesterol, and triglyceride levels.[172] However, the creatinine level increases, and all effects are negated once the drug has been discontinued.[166]

Canakinumab

In 2010, an 8-week, single-blind, double-dummy, dose-ranging study showed that the selective IL-1β antibody canakinumab yielded fast and lasting relief of pain in patients with acute gouty arthritis flares refractory to treatment with NSAIDs or colchicine.[173] However, in June 2011, canakinumab was denied approval by the FDA.[174] (See FDA Panel Says No to Canakinumab for Gout Attacks.)

Diet and Activity

Because uric acid is a breakdown product of purine, high-purine foods should be either avoided or consumed only in moderation. Foods very high in purines include the following:

  • Organ meats such as sweetbreads (eg, pancreas and thymus)
  • Smelt
  • Sardines
  • Mussels

Foods moderately high in purines include the following:

  • Anchovies
  • Trout
  • Haddock
  • Scallops
  • Mutton
  • Veal
  • Liver
  • Bacon
  • Salmon
  • Kidneys
  • Turkey

Purines are found in all protein foods. All sources of purines cannot and should not be eliminated.

Overall, purine restriction generally reduces serum uric acid levels by no more than 1 mg/mL, with modest impact, and diets with very low purine content are not palatable. Diet modifications alone are rarely able to lower uric acid levels sufficiently to prevent accumulation of urate, but they may help lessen the triggers of acute gout attacks.

Patients with gout should avoid excess ingestion of alcoholic drinks, particularly beer, because alcohol use elevates uric acid levels and thus can precipitate attacks of gout. Indeed, heavy drinkers are much more likely to have recurrent gout attacks, even with allopurinol therapy. Moderate wine intake is not associated with increased development of incident gout,[1] but excesses of any form of alcohol in gout patients are associated with acute gout flares.

Patients should avoid sodas and other beverages or foods sweetened with high-fructose corn syrup. They should also limit their use of naturally sweet fruit juices, table sugar, and sweetened beverages and desserts, as well as table salt.[118] Patients taking colchicine should avoid grapefruit and grapefruit juice.

Maintaining a high level of hydration with water (at least 8 glasses of liquids per day) may be helpful in avoiding attacks of gout. In view of the association of gout with atherosclerosis, the diagnosis of gout may afford a particularly good opportunity for the clinician to advise a low-cholesterol, low-fat diet if such a diet is otherwise appropriate for the patient. Although a diet of this type may help uric acid levels, such advice should be given primarily to help prevent atherosclerosis.

Weight reduction in patients who are obese can improve hyperuricemia. Ketosis-inducing diets (eg, fasting) should be avoided, however.

Because acute attacks are already sufficiently limiting of activity, additional limitations of activity are not necessary. The patient should avoid trauma to the affected joint; otherwise, they should be active.

Consultations

Rheumatologists should be involved in the care of patients with difficult gout, as advised in the ACR guidelines. They can establish the diagnosis with arthrocentesis and synovial fluid analysis for crystals. They also are skilled in the management of this disorder, and consultation may be helpful for patients with an acute gout attack that does not respond to NSAIDs within 2 days or to colchicine within 1 day, as well as for patients with refractory hyperuricemia.

Rheumatology or orthopedic consultation is indicated for any patient with septic arthritis or for any patient in whom a septic arthritis cannot be ruled out.

Long-Term Monitoring

After diagnosis and treatment of an acute gouty arthritis episode, the patient should return for a follow-up visit in approximately 1 month to be evaluated for therapy to lower serum uric acid levels.

If uric acid–lowering therapy is begun, patients should be seen within 2 weeks to ensure that no untoward toxicity has developed and then every 1-2 months while medication dosages are adjusted to achieve the target uric acid level of 5-6 mg/dL. Once this level is achieved and maintained, patients can be seen every 6-12 months and their serum uric acid monitored to help assess efficacy and adherence.

Prevention

Diet may affect the risk of developing gout.[175] A large prospective cohort study in men found that higher adherence to the Dietary Approaches to Stop Hypertension (DASH) diet was associated with a lower risk for gout (adjusted relative risk [RR] for extreme fifths 0.68, 95% confidence interval [CI] 0.57–0.80, P for trend < 0.001), whereas following a typical Western diet was associated with an increased risk for gout (RR 1.42,  95% CI 1.16–1.74, P=0.005).[176]

The study included 44,444 men with no prior history of gout. On the basis of questionnaire responses, each participant was assigned a DASH dietary pattern score (based on high intake of fruits, vegetables, nuts and legumes, low-fat dairy products, and whole grains, and low intake of sodium, sweetened beverages, and red and processed meats) and a Western dietary pattern score (based on high intake of red and processed meats, French fries, refined grains, sweets, and desserts). Documented gout occurred in 1731 study subjects during 26 years of follow-up.[176]

As an observational trial, the study could not prove that the DASH diet reduced gout risks. In addition, 91% of the study subjects were white men, and all were health professionals, so the study results may not apply to other racial or socioeconomic groups. Nevertheless, the DASH diet is more palatable than a low-purine diet, and it offers the additional benefits of reducing the risk for cardiovascular disease, stroke, and kidney stones.[175, 176]

 

Guidelines

Guidelines Summary

Guidelines on hyperuricemia and gout have been developed by the following organizations:

  • American College of Rheumatology (ACR) – Management of hyperuricemia. [118]
  • ACR – Treatment and prophylaxis of acute gouty arthritis [119]
  • American College of Physicians (ACP) – Diagnosis of acute gout [177]
  • ACP – Management of acute and recurrent gout [143]

American College of Rheumatology Guidelines

ACR guidelines on gout use the following evidence grades for recommendations:

  • Level A – Supported by more than one randomized clinical trial or meta-analysis
  • Level B – Derived from a single randomized trial or nonrandomized studies
  • Level C – Consensus opinion of experts, case studies, or standard of care

Baseline treatment recommendations

ACR baseline recommendations for treatment of patients with gout are as follows (all evidence level C)[118] :

  • Patient education, with diet and lifestyle recommendations
  • Consider secondary causes of hyperuricemia
  • Consider elimination of nonessential prescription drugs that induce hyperuricemia
  • Clinically evaluate gout disease burden (ie, palpable tophi, frequency and severity of acute and chronic symptoms and signs)

Patient education

The ACR guidelines recommend the following general health, diet, and lifestyle measures for gout patients[118] :

  • Weight loss for obese patients, to achieve a body mass index (BMI) that promotes general health
  • Healthy overall diet
  • Exercise (achieve physical fitness
  • Smoking cessation
  • Staying well hydrated

Specific dietary recommendations are listed in Table 1, below.[118]

Table 1. American College of Rheumatology Dietary Recommendations for Gout Patients (Open Table in a new window)

Avoid

Limit

Encourage

Organ meats high in purine content (eg, sweetbreads, liver, kidney)

Serving sizes of beef, lamb, pork, and seafood with high purine content (eg, sardines, shellfish)

Low-fat or non-fat dairy products

High-fructose corn syrup–sweetened sodas, other beverages, foods

  • Servings of naturally sweet fruit juices
  • Table sugar, sweetened beverages, desserts
  • Table salts, including in sauces and gravies

Vegetables

Alcohol overuse (ie, >2 servings/day for men, >1/d for women

Alcohol—particularly beer, but also wine and spirits

 

Secondary causes of hyperuricemia

The ACR recommends the following checklist of comorbidities as appropriate to consider in the clinical evaluation of patients with gout, and to evaluate if clinically indicated (all level C)[118] :

  • Obesity, dietary factors
  • Excessive alcohol intake
  • Metabolic syndrome, type 2 diabetes mellitus
  • Hypertension
  • Hyperlipidemia, modifiable risk factors for coronary artery disease or stroke
  • Serum urate–elevating medications
  • History of urolithiasis
  • Chronic kidney, glomerular, or interstitial renal disease (eg, analgesic nephropathy, polycystic kidney disease)
  • In selected cases, potential genetic or acquired causes of uric acid overproduction (eg, inborn error of purine metabolism or psoriasis, myeloproliferative or lymphoproliferative disease)
  • Lead intoxication

Pharmacologic therapy

ACR indications for pharmacologic therapy to lower serum uric acid levels in patients with an established diagnosis of gouty arthritis include the following:

  • Tophus or tophi identified on clinical examination or imaging study (evidence A)
  • Frequent (≥2/yr) of acute gouty arthritis (evidence A)
  • Chronic kidney disease (CKD) stage ≥2 (evidence C)
  • Previous urolithiasis (evidence C)

Treatment to target

The ACR recommends treatment to target serum uric acid level, as follows:

  • The minimum serum uric acid target is < 6 mg/dL
  • A lower target (< 5 mg/dL) may be needed to improve signs and symptoms
  • Allopurinol or febuxostat is a first-line xanthine oxidase inhibitor for urate-lowering therapy (ULT) (evidence A)
  • If at least one xanthine oxidase inhibitor is contraindicated or not tolerated, probenecid is an alternative first-line agent (evidence B)

Allopurinol

ACR recommendations for use of allopurinol ULT in gout include the following:

  • Starting dosage should be no greater than 100 mg/day for any patient (evidence level B)
  • Start at 50 mg/day in patients with stage 4 or worse CKD (evidence B)
  • Gradually titrate maintenance dose upward every 2–5 weeks to appropriate maximum dose in order to treat to chosen serum uric acid target (evidence C)
  • Dose can be raised above 300 mg daily, even in patients with renal impairment, if it is accompanied by adequate patient education and monitoring for drug toxicity (eg, pruritus, rash, elevated hepatic transaminases) (evidence B)
  • Before starting allopurinol, consider testing for HLA–B*5801 in selected patients, specifically in subpopulations at higher risk for severe allopurinol hypersensitivity reaction (eg, Koreans with stage 3 or worse CKD, Han Chinese and Thai irrespective of renal function (evidence A)

Uricosuric urate-lowering therapy

ACR recommendations for use of uricosuric ULT in gout include the following:

  • Probenecid is the first choice among uricosuric agents for ULT (evidence B)
  • In gout patients with a creatinine clearance < 50 mL/min, probenecid is not recommended as first-line ULT monotherapy (evidence C)
  • Agents other than probenecid that have clinically significant uricosuric effects (eg, fenofibrate, losartan) can be useful as components of a comprehensive ULT strategy (evidence B)
  • A history of urolithiasis is a contraindication to first-line uricosuric urate-lowering monotherapy (evidence C)
  • Urinary uric acid should be measured before initiation of uricosuric ULT (evidence C)
  • Elevated urine uric acid indicative of uric acid overproduction is a contraindication to uricosuric ULT (evidence C)
  • Continue to monitor urinary uric acid during uricosuric ULT (evidence C)
  • Consider urine alkalinization (eg, with potassium citrate) with monitoring of urine pH, in addition to increased fluid intake, as a risk management strategy for urolithiasis (evidence C)

ACR recommendations for refractory disease in gout include the following:

  • Attempt upward titration of one xanthine oxidase inhibitor to its maximum appropriate dose (evidence A)
  • Febuxostat can be substituted for allopurinol or vice versa in the event of drug intolerance and adverse events, and such substitution should be considered after initial failure of upward dose titration of either drug (evidence C); however, febuxostat and allopurinol should not be used together
  • A uricosuric agent (eg, probenecid, fenofibrate, or losartan) may be added to a xanthine oxidase inhibitor (evidence B) or vice versa (evidence C)
  • Pegloticase is appropriate for patients with severe gout disease burden and refractoriness to, or intolerance of, conventional and appropriately dosed ULT (evidence A)
  • Pegloticase therapy is not recommended as first-line ULT agent

The ACR notes that the pegloticase package insert advises discontinuing other oral ULT agents during the course of pegloticase therapy. The ACR was unable to reach consensus on the appropriate duration of pegloticase therapy relative to intended and achieved decrease in symptoms and signs of gout.

Long-term management

ACR recommendations for long-term management of gout are as follows:

  • Continue gout attack prophylaxis in patients with ongoing gout manifestations (eg, ≥1 tophus on physical exam)
  • Continue regular monitoring of serum urate and monitoring for adverse effects
  • After resolution of palpable tophi and all acute and chronic symptoms of chronic gouty arthritis, continue all measures needed to maintain serum urate levels < 6 mg/dL indefinitely

Referral

Consider specialist referral in situations such as the following:

  • Unclear etiology of hyperuricemia
  • Difficulty reaching target serum urate level, particularly in patients with renal impairment who have had a trial of xanthine oxidase inhibitor treatment
  • Multiple and/or serious adverse effects from pharmacologic ULT

Prophylaxis

ACR recommendations for prophylaxis of acute gouty arthritis are as follows[119] :

● Pharmacologic anti-inflammatory prophylaxis is recommended for all gout patients when pharmacologic urate lowering is initiated, and should be continued if the patient has any clinical evidence of continuing gout disease activity and/or the serum urate target has not yet been achieved

● Oral colchicine is an appropriate first-line drug for prevention of gout attacks; with appropriate dose adjustments, it may be used in patients with CKD and those with drug interactions, unless medically contraindicated or not tolerated

● Low-dose NSAID therapy in an appropriate first-line choice for prevention of gout attacks, unless medically contraindicated or not tolerated

Treatment of acute attacks

ACR recommendations for treatment of attacks of acute gouty arthritis are as follows[119] :

● An acute gouty arthritis attack should be treated with pharmacologic therapy, started within 24 hours of onset

● Established pharmacologic ULT should be continued, without interruption, during an acute attack of gout.

● Nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, or oral colchicine are appropriate first-line options for treatment of acute gout, and certain combinations can be employed for severe or refractory attacks

The ACR recommends tailoring therapy according to the severity of the attack. For a mildly to moderately painful attack, particularly one affecting only one or a few small joints, or one to two large joints, monotherapy is recommended (evidence A). Choices for monotherapy include the following (all evidence A):

  • An NSAID
  • Systemic corticosteroids
  • Colchicine, if started within 36 hours after symptom onset
  • Supplemental topical ice, as needed

For patients with gastrointestinal contraindications or intolerance to other NSAIDs, use of selective COX-2 inhibitors available outside the United States (eg, etoricoxib) is an option (evidence A). However, these against share many adverse events with nonselective NSAIDs. Therapy with the agent available in the US, celecoxib, requires high doses and its risk-benefit ratio is currently unclear.

For severely painful attacks, particularly those that are polyarticular or affect multiple large joints, initial combination therapy is an option. Both agents are started at full—or, when appropriate, prophylactic—doses. Acceptable combinations include any of the following (evidence C):

  • Colchicine and NSAIDs
  • Oral corticosteroids and colchicine
  • Intra-articular steroids with all other modalities

In patients with an inadequate response to treatment (ie, < 20% improvement in their pain score within 24 h, or < 50% improvement at ≥24 h, the ACR recommends switching to an alternate monotherapy or considering add-on combination therapy (both evidence C). If the attack still fails to respond, off-label use of investigational agents may be considered (eg, interleukin-1 inhibitors such as anakinra, canakinumab, or rilonacept).

American College of Physicians Guidelines

Diagnosis of acute gout

The ACP guideline recommends using synovial fluid analysis when clinical judgment indicates that diagnostic testing is necessary in patients with possible acute gout (weak recommendation, low-quality evidence). The guideline advises that synovial fluid analysis is considered the reference standard for gout diagnosis but may be difficult to perform in a primary care setting. Synovial fluid analysis is recommended if the following criteria can be met[177]

  • An experienced clinician can aspirate the joint without substantial patient discomfort and can minimize the risk of infection
  • A reliable and accurate source (including a trained operator with a polarizing microscope) is available to assess the fluid for the presence of urate crystals
  • The clinical situation is ambiguous and a probability of joint infection exists

If the criteria for synovial fluid analysis cannot be met, the ACP recommends that clinicians either refer the patient to a source that can meet the criteria or use their clinical judgment regarding the need for joint aspiration. Clinical judgment is especially appropriate in situations that are less clinically ambiguous and the probability of infection is not significant. For example, a patient with podagra, appropriate risk factors (eg, age), and no sign of an overlying skin wound) could be considered to have gout without undergoing joint aspiration.

The ACP notes that algorithms for clinical diagnosis of gout exist and have sensitivities and specificities >80%, but little evidence exists that they can be used to identify septic joints. Current evidence is insufficient to support the use of dual-energy computed tomography or ultrasonography to diagnose acute gout.[177]

Management of acute and recurrent gout

ACP recommendations for the treatment of acute and recurrent gout attacks are as follows[143] :

  • Use corticosteroids, NSAIDS, or colchicine to treat acute gout
  • Use low-dose colchicine (1.2 mg, then 0.6 mg 1 hr later) when using colchicine for acute gout
  • Recommend against initiating long-term urate-lowering therapy in most patients after a first gout attack or in patients with infrequent attacks
  • Discuss benefits, harms, costs, and individual preferences with patients before initiating urate-lowering therapy, including concomitant prophylaxis, in patients with recurrent gout attacks

In contrast to American College of Rheumatology recommendations, the ACP concluded that evidence was insufficient to determine whether the benefits of escalating urate-lowering therapy to reach a serum urate target outweigh the harms associated with repeated monitoring and medication escalation.[143]

 

 

 

Medication

Medication Summary

Acute inflammation due to gout can be treated with nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, or colchicine. NSAIDs are the most commonly used drugs in acute gout.

Over the long term, gout is treated by decreasing tissue stores of uric acid with the xanthine oxidase inhibitors allopurinol or febuxostat or with the uricosuric agent probenecid. Because agents that lower uric acid can precipitate attacks of gout, low-dose colchicine is typically used as prophylaxis (usually for 6 months) when such therapy is initiated.

If these measures, along with adjustment of contributing medications (eg, diuretics), do not result in appropriate reduction of serum uric acid levels, uric acid−lowering treatment is escalated as recommended in the 2012 American College of Rheumatology (ACR) gout guidelines.[118, 119]

Other agents lower uric acid levels as a secondary effect. The angiotensin-receptor blocker (ARB) losartan is moderately uricosuric at 50 mg/day. The lipid-lowering agent fenofibrate reduces serum urate 19% and increases clearance by 36% at 200 mg/day.[45]

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

Class Summary

As a class, NSAIDs are the drugs most widely used to treat the pain and inflammation of acute gout attacks in patients who can safely take these medications. Although NSAID effects on pain tend to be patient-specific, naproxen and indomethacin are common choices. Nevertheless, the choice of an NSAID is a matter more of habit than of science. Use of concomitant gastric protection with misoprostol or consideration of a cyclooxygenase-2 (COX-2)–specific NSAID might be considered if the patient has gastrointestinal (GI) risk or is older than 51 years.

To control the attack as quickly and safely as possible (recalling that it takes 5 half-lives to reach steady state), consider using an NSAID with a short half-life (eg, ketoprofen, ibuprofen, or diclofenac). Use the maximum dosage of NSAID, and taper over approximately 10-14 days, depending on patient response.

Naproxen (Aleve, Mediproxen, Naprelan, Naprosyn, EC-Naprosyn)

Naproxen is used for relief of mild to moderate pain. It inhibits inflammatory reactions and pain by decreasing activity of the enzyme cyclooxygenase, which in turn decreases prostaglandin synthesis.

Ketoprofen

Ketoprofen is used for the relief of mild-to-moderate pain and inflammation. Small doses are initially indicated in small and elderly patients and in those with renal or liver disease. Individual doses greater than 75 mg do not increase therapeutic effects. Administer high doses with caution, and closely observe the patient for response.

Diclofenac (Dyloject, Zorvolex, Zipsor, Cambria)

Diclofenac inhibits prostaglandin synthesis by decreasing activity of the enzyme cyclooxygenase, which in turn decreases formation of prostaglandin precursors.

Indomethacin (Indocin, Tivorbex)

Indomethacin has been the NSAID traditionally used to treat acute inflammation in gout, though other NSAIDs are effective in this setting as well. Like all NSAIDs, indomethacin blocks cyclooxygenase and thereby reduces the generation of prostaglandins.

Celecoxib (Celebrex)

Unlike most NSAIDs, which inhibit both COX-1 and COX-2, the selective COX-2 inhibitor celecoxib offers the possibility of relieving inflammation and pain, but with a lower risk of GI side effects. It has been suggested that COX-2 expression in monocytes is induced in response to urate crystals.

Several studies have found that selective COX-2 inhibitors are comparable to other NSAIDs for treating acute gouty arthritis. However, celecoxib requires particularly high doses to provide pain relief comparable to that provided by indomethacin in acute gout.[108]

Selective COX-2 inhibitors may increase the risk of cardiac disease; 1 drug in this class, rofecoxib, was removed from the market for this reason. Celecoxib has been under investigation for associated risk of accelerated cardiac disease. Curiously, the risk appears to be associated with ingestion of 200 mg twice daily, but not with ingestion of 400 mg once daily.

Uricosuric Agents

Class Summary

Uricosuric agents lower uric acid levels by inhibiting renal tubular reabsorption of uric acid, thereby increasing net renal excretion of uric acid. These agents increase the risk of renal stones, with about a 9-10% risk for probenecid. They should not be started during an attack of acute gouty arthritis. The goal of therapy is to lower serum uric acid to approximately 5-6 mg/dL without causing renal stones.

Colchicine (Colcrys, Mitigare)

Colchicine inhibits microtubules and may thereby inhibit phagocytosis, neutrophil mobility, and chemotaxis. It also may inhibit generation of prostaglandins. The traditional approach of giving colchicine until vomiting or diarrhea appears is not appropriate; these are signs of toxicity. Instead, 1.2 mg is given orally, followed by 0.6 mg after 1 hour. Dose reduction is required for coingestion of interacting drugs (eg, P-gp or CYP3A4 inhibitors).

Probenecid

Probenecid lowers tissue stores of uric acid by increasing net renal excretion of uric acid through inhibition of tubular reabsorption. Some authorities recommend alkalizing the urine when starting probenecid to reduce the risk for renal stone formation. Probenecid is indicated for long-term management of hyperuricemia associated with gout.

Corticosteroids

Class Summary

Corticosteroids are potent and effective anti-inflammatory drugs that can be used to treat acute gout in patients who cannot tolerate NSAIDs or colchicine. They can be given orally, intramuscularly (IM), intravenously (IV), or intra-articularly. Adrenocorticotropic hormone (ACTH) also acts in gout, in part by inducing adrenal steroids. No intrinsic advantage to treating with IV corticosteroids exists unless the patient cannot take oral medications.

The short-burst corticosteroid regimen used to treat an acute flare of gout is generally well tolerated. Nevertheless, patients may experience the adverse effects seen with long-term steroid use.

In patients with only 1 or 2 involved joints, intra-articular corticosteroids are a safe and effective treatment option, once infection has been excluded. Water-soluble steroids (eg, dexamethasone) are teleologically inappropriate for use as a depot steroid treatment.

Prednisone (Deltasone, Prednisone Intensol, Rayos)

Oral prednisone can be given to abort an attack of gout. By reversing increased capillary permeability and suppressing polymorphonuclear leukocyte (PMN) activity, this agent may decrease inflammation. Steroid dose packs that clearly label the dose to be taken each day can be convenient for some patients.

Triamcinolone (Kenalog, Zilretta)

Intra-articular use is considered by some as the treatment of choice for pseudogout and for acute gouty attacks in patients who cannot be given NSAIDs, colchicine, or high-dose systemic corticosteroids.

Corticotropin (HP Acthar)

Corticotropin stimulates endogenous production of corticosteroids and directly and rapidly acts on peripheral leukocyte activation. It decreases inflammation by suppressing migration of PMNs and reversing increased capillary permeability.

Xanthine Oxidase Inhibitors

Class Summary

Inhibition of xanthine oxidase, the enzyme that synthesizes uric acid from hypoxanthine, reduces the synthesis of uric acid without disrupting the biosynthesis of vital purines. This results in the reduction of the tissue stores of uric acid. The goal of therapy is to lower the serum uric acid level to approximately 5-6 mg/dL. These agents should not be started during an attack of acute gouty arthritis without adequate control of the gouty inflammation.

Allopurinol (Zyloprim, Aloprim)

Allopurinol reduces production of uric acid, thereby allowing the body to dispose of excess uric acid stores. It is the most effective therapy for lowering serum uric acid. Most patients achieve the target uric acid level of 5 mg/dL at a dosage of 300-400 mg/day. A lower dosage is used if renal insufficiency is present.

Febuxostat (Uloric)

Febuxostat is a potential alternative to allopurinol.[126, 127] Like allopurinol, febuxostat is a xanthine oxidase inhibitor that prevents uric acid production and lowers elevated serum uric acid levels. Unlike allopurinol, it is a thiazolecarboxylic acid derivative, not a purine base analogue. Febuxostat physically blocks the channel to the molybdenum-pterin active site of xanthine oxidase and is metabolized by liver oxidation and glucuronidation.[42]

Common adverse events include upper respiratory tract infections, arthralgias, diarrhea, headache, and liver function abnormalities. Atrioventricular block or atrial fibrillation and cholecystitis also have been reported.[141] As with other uricosuric agents, initiation of febuxostat may precipitate gouty attacks.[42, 141]

Selective Uric acid Reabsorption Inhibitor (SURI)

Class Summary

May consider adding a SURI to the therapeutic regimen in patients who have not achieved target serum uric acid levels with a xanthine oxidase inhibitor alone.

Lesinurad (Zurampic)

Lesinurad is the first selective uric acid reabsorption inhibitor to be approved in the United States. It acts by inhibiting the urate transporter, URAT1, which is responsible for the majority of the renal reabsorption of uric acid. It also inhibits organic anion transporter 4 (OAT4), a uric acid transporter associated with diuretic-induced hyperuricemia. It is indicated in combination with a xanthine oxidase inhibitor for hyperuricemia associated with gout in patients who have not achieved target serum uric acid levels with a xanthine oxidase inhibitor alone.

Rheumatologics, Other

Class Summary

Uricase facilitates conversion of urate to allantoin. Unlike uric acid, allantoin is soluble and easily excreted by the kidneys. Thus, hyperuricemia is reduced, with little risk of acute kidney injury.

Pegloticase (Krystexxa)

Pegloticase is a pegylated uric acid–specific enzyme that is a polyethylene glycol conjugate of recombinant uricase. It achieves its therapeutic effect by catalyzing oxidation of uric acid to allantoin, thereby lowering serum uric acid levels. Pegloticase is indicated for gout in adults refractory to conventional therapy (ie, when serum uric acid levels have not normalized and either signs and symptoms are inadequately controlled with xanthine oxidase inhibitors or uricosurics at maximum appropriate doses or xanthine oxidase inhibitors are contraindicated).

The dosage is 8 mg IV every 2 weeks. Complications include anaphylaxis, infusion reactions, flare of gout attacks in 63-86% of patients and nephrolithiasis in 13-14%, along with arthralgias, nausea, dyspepsia, muscle spasms, pyrexia, back pain, diarrhea, and rash.[142, 143] Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a contraindication.[143]

Corticotropic Hormones

Class Summary

Corticotropic hormones stimulate synthesis and release of corticosteroid hormones. They are principally used in diagnostic tests to differentiate primary adrenal insufficiency from secondary adrenal insufficiency. They have limited therapeutic value in conditions responsive to corticosteroid therapy, for which a corticosteroid should be the drug of choice.

Cosyntropin (Cortrosyn)

Cosyntropin is an adrenocorticotropic hormone (corticotropin) that stimulates the production and release of endogenous steroids. It is an effective treatment of acute crystal-induced arthritis in postoperative patients and in other patients who cannot take oral medications.

Combination drugs

Class Summary

Uricase facilitates conversion of urate to allantoin. Unlike uric acid, allantoin is soluble and easily excreted by the kidneys. Thus, hyperuricemia is reduced, with little risk of acute kidney injury.

Gout is a highly symptomatic and painful form of inflammatory arthritis caused by hyperuricemia, or elevated serum uric levels in the blood, which can lead to painful flares and serious potential long-term health consequences. Combination treatments provide a new option in the treatment of both gout and hyperuricemia.

Lesinurad/allopurinol (Duzallo)

Fixed-dosed combination indicated for treatment of hyperuricemia associated with gout in patients for whom target serum uric acid (sUA) levels have not been achieved with allopurinol alone.

 

Questions & Answers

Overview

What is the difference between gout and pseudogout?

What are the symptoms of gout and pseudogout?

What are the physical findings of gout and pseudogout?

What are the complications of gout?

Which studies may be helpful in the diagnosis of gout and pseudogout?

What are the typical characteristics of erosions in gout?

Which ultrasonographic findings indicate gout?

Other than ultrasonography, which imaging studies are used to evaluate gout?

How is gout managed?

What agents are used in the treatment of acute crystal-induced arthritis in gout?

Which agents are used to lower uric acid levels in gout?

Which therapeutic agents may be considered in the treatment of gout?

What dietary changes may be beneficial in the treatment of gout and pseudogout?

What are gout and pseudogout?

What are the likely complications if gout is left untreated?

What are the risk factors for developing gout?

What is the difference between primary and secondary gout?

How is gout diagnosed?

What is the prognosis of gout?

How are gout and pseudogout managed?

What is the pathogenesis of gout?

What is the pathogenesis of pseudogout?

Where are urate crystals found in patients with gout?

What triggers a gout attack?

How does gout develop?

Why do excess urate stores develop in gout?

What causes secondary gout due to underexcretion of uric acid?

What comorbid conditions increase the risk of developing gout?

Which foods increase the risk of gout?

Is gout a genetic disorder?

Which genes are associated with an increased risk of gout?

What are the major causes of gout in developed countries?

What triggers gout flares?

How do the underlying causes of gout and pseudogout differ?

What are the risk factors for development of pseudogout?

What genetic or environmental factors are responsible for pseudogout?

What is the prevalence of gout in the US?

At what age does pseudogout become increasingly common?

Are gout attacks seasonal?

What is the global prevalence of gout?

Are gout and pseudogout more common in men or women?

How does the prevalence of gout differ among age groups?

What causes early onset of gout?

Does gout have a racial predilection?

What is the general prognosis of gout?

What is the prognosis of gout with early treatment?

What is the prognosis of untreated chronic tophaceous gout?

What is the prognosis of acute attacks of pseudogout?

Which diseases are associated with hyperuricemia and gout?

Are mortality rates increased in patients with gout?

Are vascular or cardiovascular risk increased in patients with gout?

What dietary restrictions are advisable for gout?

Presentation

What medical history indicates gout?

Where are the most common sites of gout arthritis?

Where are the most common sites of pseudogout arthritis?

Can gout and pseudogout be polyarticular?

How long do symptoms of untreated acute gout last?

How often does gout initially present as polyarticular arthritis?

Do the symptoms of untreated gout change over time?

What triggers acute flares of gout?

Does gout increase the risk of developing renal stones?

What metabolic disorders are common comorbidities of gout?

What comorbid conditions complicate the use of medications to treat gout?

How is crystal-induced arthritis differentiated from cellulitis or septic arthritis in suspected gout?

Which joints should be examined in cases of gout or pseudogout?

Which physical findings of the joints indicate gout?

What are tophi and how are they associated with gout?

What is the typical presentation of tophi in gout?

Does gout affect the eye?

What are complications of gout?

DDX

What are the diagnostic criteria for gout?

Which disorders should be considered in the differential diagnoses of gout and pseudogout?

What are the differential diagnoses for Gout and Pseudogout?

Workup

What is the role of arthrocentesis in the evaluation of suspected gout?

How do the crystals of gout and pseudogout appear on microscopic analysis?

What is the importance of WBC count in synovial fluid during the evaluation of suspected gout or pseudogout?

Does an elevated serum uric acid level confirm a diagnosis of acute gout?

What should be included in the evaluation of pseudogout in an initial attack of arthritis with calcium pyrophosphate (CPP) crystals?

How does an acute attack of gout affect the WBC count and the erythrocyte sedimentation rate?

Which imaging studies are indicated in the evaluation of suspected gout or pseudogout?

Is synovial fluid analysis useful in the diagnosis of gout and pseudogout?

Which synovial fluid analysis findings confirm a diagnosis of gout or pseudogout?

What is the sensitivity and specificity of synovial fluid analysis in the diagnosis of gout?

What WBC count in synovial fluid indicates gout?

What do synovial fluid glucose levels indicate in regard to gout?

Can crystalline arthritis and infectious arthritis coexist in patients with gout?

How are pathologic specimens of synovial fluids processed in the workup of gout?

Are repeat joint aspirations needed once a diagnosis of gout is established by confirmation of crystals?

Should serum uric acid testing be used in the diagnosis of gout?

Should asymptomatic hyperuricemia be treated in patients with gout?

Does the level of serum uric acid correlate with risk of developing gout?

How is urinary uric acid evaluation used in the diagnosis of gout and pseudogout?

Are blood studies useful in the diagnosis of gout and pseudogout?

Is radiography useful in the diagnosis of gout and pseudogout?

What are characteristics of erosions typically found in gout?

What ultrasonographic findings indicate gout?

What is the sensitivity of the double contour sign for crystalline arthritis, gout, and calcium pyrophosphate deposition disease?

Is ultrasonography or radiography more sensitive in the detection of calcium pyrophosphate crystal deposition (CPPD)?

Can ultrasonography identify urate crystal deposition in asymptomatic gout?

Can ultrasonography detect tendon involvement in gout?

How is CT scanning used in the diagnosis of gout?

How is MRI used in the diagnosis of gout?

What are the histological findings of gout?

What are the histological findings of pseudogout?

Treatment

How is gout managed?

Do guidelines exist for the management of gout?

How is asymptomatic hyperuricemia treated?

Does urate-lowering therapy decrease the risk of kidney damage in gout?

Does urate-lowering therapy increase the risk of gout flares?

What are common risk factors for gout flares?

Is prophylaxis against gout flares required during the first year of urate-lowering therapies?

What are the indications for surgical removal of tophi with gout?

What are the treat-to-target recommendations for gout?

How does the treatment of pseudogout differ from the treatment of gout?

Should gout or pseudogout be treated without a proven diagnosis?

What are options for the treatment of acute gout?

How is hyperuricemia managed in gout?

When should NSAIDS be used in the treatment of gout?

What is the appropriate dosage of NSAIDS for controlling acute attacks of gout?

Is colchicine effective in the treatment of acute gout?

What are the dosage and regimen recommendations for colchicine in the treatment of acute gout?

When should colchicine be avoided as treatment for acute gout?

Is a clinical response to colchicine pathognomonic for gout?

Is IV colchicine available in the US?

When should corticosteroids be considered in the treatment of acute gout?

Which corticosteroid regimens are recommended for acute gout?

Which combination therapies may be considered for acute gout?

How is lesinurad (Zurampic) used in the treatment of chronic gout?

How should the first attack of gout be treated?

What is the risk of a recurrent attack of gout?

What are the ACR guidelines for urate-lowering therapy in gout?

What is the goal of the long-term management of gout?

Are there guidelines that do not recommend the "treat-to-target" approach to controlling serum uric acid levels in gout?

Which medications should be avoided in gout?

How is underexcretion of uric acid treated in gout?

What are the ACR treatment guidelines for gout in patients with renal disease?

What are the prophylactic treatments for gout?

What are the recommended dosages of colchicine for prophylaxis of gout?

What are the possible adverse effects of colchicine for prophylaxis of gout?

Should uric acid–lowering therapy be discontinued if a gout flare develops?

What is the role of allopurinol in the treatment of chronic gout?

What are the possible adverse effects of allopurinol?

Which patients with gout are at increased risk of developing severe allopurinol hypersensitivity syndrome?

What is the recommended dosage of allopurinol in the treatment of chronic gout?

Which drug interactions should be considered prior to prescribing allopurinol in patients with gout?

What is the likelihood of treatment compliance in patients with gout who are prescribed allopurinol and how can it be improved?

How is febuxostat used in the treatment of chronic gout?

What is the efficacy and safety of febuxostat in lowering hyperuricemia?

What is the efficacy and safety of febuxostat in lowering hyperuricemia in patients aged 65 years or older?

What is the efficacy and safety of febuxostat in lowering hyperuricemia in black patients?

What is the efficacy and safety of febuxostat in lowering hyperuricemia in women?

What is the efficacy of lesinurad in the treatment of gout?

How is nonrecombinant urate-oxidase (uricase) used in the treatment of chronic gout?

What are the potential adverse effects of pegloticase?

Is benzbromarone safe to use in the treatment of gout?

Is vitamin C effective in the treatment of gout?

Is the interleukin (IL)-1 antagonist anakinra effective in the treatment of gout?

Is fenofibrate an effective treatment for gout?

Is canakinumab FDA approved for the treatment of gout?

What foods high in purines should be avoided by patients with gout?

Are diet modifications successful in reducing uric acid levels in gout?

Should patients with gout drink alcohol?

Should sugar and salt be restricted in gout?

How does hydration affect gout?

Is weight reduction helpful for gout?

Should physical activity be restricted in gout?

When should consultations be considered for gout?

What monitoring should be performed in gout?

Can diet affect the risk for development of gout?

Guidelines

What are the evidence grades used in ACR guidelines for gout?

What are the ACR treatment guidelines for gout?

What are the ACR guidelines for general health, diet, and lifestyle measures in patients with gout?

What comorbidities do the ACR guidelines recommend as considerations in the clinical evaluation of gout?

What are the ACR guidelines for medication therapy in gouty arthritis?

What are the ACR guidelines for treatment to target serum uric acid levels in gout?

What are the ACR guidelines for the use of allopurinol ULT in gout?

What are the ACR guidelines for the use of uricosuric urate-lowering therapy (ULT) in gout?

What are the ACR treatment guidelines for refractory gout?

What are the ACR guidelines for long-term management of gout?

When should referral to a specialist be considered in gout?

What are the ACR guidelines for prophylaxis of acute gout?

What are the ACR guidelines for treatment of acute gout arthritis?

What are the ACP guidelines for the diagnosis of acute gout?

What are the ACP guidelines for the treatment of acute and recurrent gout?

Medications

Which medications are used in the treatment of gout and pseudogout?

Which medications in the drug class Nonsteroidal Anti-inflammatory Drugs (NSAIDs) are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Uricosuric Agents are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Corticosteroids are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Xanthine Oxidase Inhibitors are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Selective Uric acid Reabsorption Inhibitor (SURI) are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Rheumatologics, Other are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Corticotropic Hormones are used in the treatment of Gout and Pseudogout?

Which medications in the drug class Combination drugs are used in the treatment of Gout and Pseudogout?