History
Q fever is a protean disease that lacks a distinct clinical presentation. Almost 50% of patients are asymptomatic. Symptomatic infection is more common in adults than in children and is more common in men than in women. Common presentations vary geographically. For example, in the Basque region of northern Spain, pneumonia is a common finding, whereas in southern Spain, hepatitis predominates.
The primary factor leading to the identification of Q fever is the epidemiologic circumstance: a history of exposure, particularly occupational exposure, exposure to parturient animals or their newborn, or tick bites.
Most common symptoms include fever.
Acute Q fever
Sixty percent of patients with Q fever are asymptomatic, and others may have mild disease. The incubation period varies from 2 to 6 weeks (range, 14-39 d; average, 20 d). The 3 main clinical presentations are as follows [3, 15, 19] :
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A self-limited, influenzalike febrile illness (up to 40°C) (88-100%) of abrupt onset, which is often accompanied by headache (68-98%) (typically retrobulbar), myalgia (47-69%) (arthralgia is uncommon), chills (68-88%), fatigue (97-100%), and sweats (31-98%); the temperature returns to normal within 5-14 days
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Pneumonia (predominant in North America), usually mild in nature (crackles auscultated in 50% of cases) or as an incidental radiographic finding; when there is respiratory involvement, patients have a dry, nonproductive cough (24-90%), dyspnea, and pleuritic chest pain; this condition rarely is fulminant but occasionally progresses to acute respiratory distress syndrome (ARDS)
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Hepatitis (predominant in Europe), usually with mild elevation of transaminases (2-3 times the reference range) and may be associated with antismooth muscle, antiphospholipid, or antinuclear antibodies; jaundice and acute gastrointestinal (GI) symptoms (nausea and vomiting, diarrhea [rare], right upper quadrant abdominal pain) are rare; manifestations resolve within 2-3 weeks.
Cardiovascular and neurologic manifestations develop in approximately 1% of patients and include pericarditis, myocarditis, acute endocarditis, and meningoencephalitis. A dissociation between heart rate and temperature occurs in one third of cases, some patients with acute Q fever pericarditis report chest pain, patients with myocarditis may experience palpitations, chest pain, or dyspnea. Rarely, individuals with acute Q fever may develop endocarditis, which appears to be an autoimmune complication of early infection and may be associated with antiphospholipid antibody syndrome. These cases may be associated with an IgG anticardiolipin antibody level of more than 100 immunoglobulin G-type phospholipid units. [20, 21, 22] Q fever endocarditis appears to occur primarily in men or in those who are older than 40 years, who are pregnant, who are immunocompromised, and/or who have underlying valvular disease. [23]
The 3 major neurologic syndromes of Q fever are meningoencephalitis or encephalitis, meningitis, and myelitis and peripheral neuropathy. Other neurologic symptoms may include headache, confusion, and neck stiffness. Persistent Q fever has been associated with ischemic stroke in elderly patients. [24]
Dermatologic manifestations in the form of erythema nodosum or other nonspecific exanthemas, maculopapular rash, or diffuse punctiform pruritic rash may be associated with acute disease. Rash is not a typical feature of Q fever, but skin manifestations have been reported in up to 20% of French patients. [19]
Obstetric manifestations include spontaneous abortion. Rare presentations have included thyroiditis, mediastinal lymphadenopathy, pancreatitis, mesenteric panniculitis, epididymitis, orchitis, priapism, inappropriate secretion of antidiuretic hormone (SIADH), optic neuritis, Guillain-Barré syndrome, and extrapyramidal neurologic disease. Acute Q fever in pregnancy is more likely to be asymptomatic and to result in chronic infection than is acute Q fever in nonpregnant women.
Chronic Q fever
Among patients with acute infection, 0.2% to 1.4% may develop chronic infection, but few data are available regarding this. Chronic infection (defined as infection lasting longer than 6 months) may not manifest until months or even years after acute infection. [3, 15, 19]
Endocarditis with negative culture findings and seropositivity (culture positivity and seropositivity or culture negativity and seronegativity are relatively uncommon) is the main clinical presentation of chronic Q fever, usually occurring in patients with preexisting cardiac disease including valve defects, rheumatic heart disease, and prosthetic valves. Patients in immunocompromised states (eg, due to acquired immunodeficiency syndrome [AIDS], renal failure, hematologic cancer [including lymphoma], and long-term corticosteroid use) also are susceptible. Patients may present with heart failure or nonspecific symptoms, including low-grade fever, fatigue, chills, arthralgia, dyspnea, rash from septic thromboembolism, and night sweats.
Other systemic manifestations include the following:
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Vascular (infections of aneurysms, grafts, prostheses)
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Obstetric (spontaneous abortion, premature labor [likely due to placentitis])
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Hepatic (chronic hepatitis [usually associated with endocarditis])
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Neurologic (mononeuritis, optic neuritis [6] )
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Pulmonary (interstitial fibrosis, pseudotumor)
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Renal (glomerulonephritis)
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Hematologic malignancy (B-cell lymphoma [26] )
Chronic fatigue syndrome has been described in approximately 10%-20% of patients, more than 6 months following acute Q fever. In addition, C burnetii could be added to the organisms involved in TORCH syndrome (toxoplasmosis, other infections, rubella, cytomegalovirus infection, and herpes simplex). [27]
Physical Examination
Specific physical findings may be absent in acute Q fever. When present, physical findings vary with the clinical presentation. In chronic Q fever, findings consistent with endocarditis and hepatitis are more frequently found. Aseptic meningitis/encephalitis occurs in approximately 1% of acute and chronic Q fever cases.
Acute Q fever
Signs of acute Q fever may include the following:
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Pneumonia: High-grade fever and nonspecific crackles, rales, rhonchi, or wheezing; dry cough, pleuritic chest pain, dyspnea, tachypnea; less frequently, signs of consolidation or pleural effusion
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Isolated fever: Fever may be low grade but is usually as high as 40°C
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Hepatitis: Hepatomegaly or, in rare cases, jaundice; fever, malaise, right upper quadrant abdominal pain may be present
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Meningeal signs, pericardial rub (pericarditis), and signs of heart failure may be present; tachycardia, an irregular pulse, and a gallop rhythm (myocarditis)
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Meningitis or encephalitis (rare, approximately 1%): Severe headache, stiff neck, fever
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Nonspecific exanthemas (20%), most commonly a maculopapular rash on the trunk; erythema nodosum has also been described
Chronic Q fever
Endocarditis is the most common presentation of chronic disease and manifests as low-grade fever (or no fever), augmentation of a known heart murmur, signs of heart failure, hepatosplenomegaly and splenomegaly (approximately 50%), jaundice (occasional), clubbing, arterial emboli (approximated 33%), vegetations on any valve (although aortic and prosthetic valves are favored), and purpuric rash (approximately 20%). [3] The aortic and mitral valves are more often involved.
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A: Chest radiograph with normal findings. B: Chest radiograph demonstrating Q fever pneumonia.
