Fabry Disease Overview of Fabry Disease

Fabry disease is an X-linked lysosomal disorder that leads to excessive deposition of neutral glycosphingolipids in the vascular endothelium of several organs and in epithelial and smooth muscle cells. Progressive endothelial accumulation of glycosphingolipids accounts for the associated clinical abnormalities of skin, eye, kidney, heart, brain, and peripheral nervous system.

When young patients present with signs and symptoms of a stroke, along with a history of skin lesions, renal insufficiency or failure, and heart attacks, Fabry disease is a consideration.

Fabry disease is uncommon, although research suggests that Fabry mutations may be more frequent than previously thought in cryptogenic stroke patients. However, the patients studied invariably had other signs of Fabry disease, including proteinuria and acroparesthesias.^[1]

The diagnosis of Fabry disease has considerable implications regarding treatment, management, and counseling. Specifically, physicians may be alert to the involvement of other organs besides those of the central nervous system (CNS), thus making early intervention possible. With early identification, counseling and prenatal diagnosis may be offered to family members.^[2]

Treatment and diagnostic considerations

Patients with Fabry disease seek care from a variety of specialists, usually because of the involvement of a number of organ systems.

The diagnosis and treatment of Fabry disease can be challenging. The signs and symptoms of Fabry disease may be nonspecific, and if manifestations in different organs are considered in isolation, the unifying diagnosis may be missed.^{[3, 4]}

If the family history suggests a diagnosis of Fabry disease, genetic testing and counseling should be offered to all family members, regardless of their sex.

Aggressive efforts to diagnose the etiology of stroke are necessary to plan secondary prevention strategies. In this context, unusual presentations, with multiple organ involvement or lack of traditional vascular risk factors, should lead to the consideration of Fabry disease. Traditional secondary stroke prevention strategies are still necessary.

Treatment strategies involve combined efforts from multiple specialties. The diagnosis and care of these patients usually is best handled at tertiary care centers.

Acute strokes may be managed adequately in community hospitals in the initial phases. Further care can be accomplished by means of consultation with tertiary care centers.

Research to replenish deficient enzymes by means of gene transfer via adenovirus is in its early stages.

For patient education information, see eMedicine's Stroke Center, as well as Stroke.

Go to Stroke, Ischemic, for more complete information on this topic.

Deficiency of alpha-galactosidase A activity leads to lysosomal accumulation of glycosphingolipids, predominantly the cerebroside trihexosides. Diffuse, abnormal accumulation of glycosphingolipids occurs in all tissues, producing swelling and proliferation of endothelial cells. Abnormal reactivity of endothelial cells, with changes in blood flow in the brain and in peripheral vessels, has been documented on magnetic resonance imaging (MRI), positron emission tomography (PET) scanning, transcranial Doppler imaging (TCD), and plethysmography.^[5]

Disturbances in intraluminal pressure and angioarchitecture are thought to lead to dilatation, angiectasia, and dolichoectasia. The vertebrobasilar arteries appear particularly susceptible to dilatational arteriopathy. Small penetrating arteries frequently become narrowed and occluded. Cerebral infarcts result from direct vascular occlusion or stretching and from the distension of branches of the dolichoectatic parent vessels.

Decreased levels of thrombomodulin (TM) and increased plasminogen activator inhibitor (PAI) have been found in Fabry disease patients, thus suggesting that a prothrombotic state may be one cause of stroke in these patients.

The precise cause of increased incidence of stroke has not been established. Findings that could contribute to this increased risk include abnormal nitric oxide and non-nitric oxide dependent endothelial dilation and abnormal endothelial nitric oxide synthase (eNOS) activity leading to aberrant vascular functioning. Paradoxical hyperperfusion is seen in strokelike lesions whose significance is not known.^[6]

Nonischemic, compressive complications of dolichoectatic intracranial arteries include hydrocephalus, optic atrophy, trigeminal neuralgia, and cranial nerve palsies.

The prevalence of Fabry disease has been previously estimated to be 1 per 40,000 people. Most of the patients are white, but it is also found in African Americans and in persons of Hispanic or Asian descent.

A prospective, multicenter study of cryptogenic strokes from Germany suggested that the prevalence of Fabry disease could be as high as 1.2%.^[7] This would mean that the prevalence rate is higher than that for mutations of factor V Leiden.

Because Fabry disease affects several organ systems, morbidity and mortality are related to the combined effects of renal failure, heart failure, and stroke.

The rate of stroke is reportedly 10-24%. However, this rate may be an overestimation, because the data are from tertiary referral centers. About 70% of cerebral infarcts are in the vertebrobasilar circulation; most of the remainder involves the perforating arteries in the anterior circulation. Intracranial hemorrhage is rare.

Recurrence of cerebrovascular events is common, and lesion load (measured radiologically) increases with advancing age.

Left ventricular hypertrophy, conduction defects, valvular deficiencies, and myocardial infarctions are cardiac manifestations of disease in some patients.

Proteinuria and progressive renal failure are a result of glycosphingolipid accumulation in the renal glomeruli and tubules.

Hemiparesis, vertigo, diplopia, dysarthria, hemianopia, sensory loss, and other typical stroke symptoms characterize CNS involvement.

Death, as a result of renal failure, heart failure, or strokes, commonly occurs by the fourth or fifth decade of life.

After a first stroke, recurrent stroke is frequent, with a median interval to first recurrence of 6.4 years in hemizygotes.

Fabry disease follows X-linked genetics, manifesting predominantly in men. However, female heterozygotes also present with clinical and laboratory features of Fabry disease.

Different investigators have reported that the mean age of hemizygotic men at the onset of symptomatic stroke is 29-38 years. The mean age of female heterozygotes at the onset of symptomatic strokes is 40-43 years.

Other symptoms and signs of Fabry disease may be present in male children as young as age 9 years and in females by age 13 years.

Hypertension occurs with increased frequency in patients with Fabry disease because of progressive renal impairment. Other traditional risk factors for stroke, such as diabetes, hypercholesterolemia, and smoking, may or may not be present in these patients.

Because Fabry disease has an X-linked genetic inheritance pattern, the patient’s family history may be positive for the condition.

The diffuse involvement of different organ systems in Fabry disease leads to a number of abnormalities that can be discovered on physical examination.

Abundant punctate, nonblanching, dark red to blue-black clusters of ectatic blood vessels may be found just below the skin. The clusters develop in different parts of the body, although they are most commonly found in a bathing-trunk distribution. The clusters are known as angiokeratomas, although they are also referred to as angiokeratoma corporis diffusum universale.

Lenticular opacities and vascular lesions of the conjunctiva and retina may be present.

Cardiomegaly and rhythm abnormalities may be evident on chest palpation and auscultation.

Vague complaints of pain in hands and feet may be a presenting feature. These symptoms are called acroparesthesias, as they reflect the peripheral neuropathy that is a frequent manifestation of the disease. This pain may be both episodic and chronic. Acute episodes may be triggered by exposure to extremes of temperature, stress, emotion, and/or fatigue.

Fabry disease must be high on the list of differential diagnoses when a young man presents with signs and symptoms of stroke, along with other characteristic lesions.

Conditions that mimic the symptoms of Fabry disease include the following:

• Acute Stroke Management
• Basilar Artery Thrombosis
• Cardioembolic Stroke
• Cavernous Sinus Syndromes
• Dissection Syndromes
• Lacunar Syndromes
• Posterior Cerebral Artery Stroke
• Transient Global Amnesia

Microscopic examination of urine may show lipid-laden epithelial cells.

Electrolyte imbalances reflecting renal failure may be seen.

When an acute stroke is suspected on clinical grounds, customary laboratory tests, such as determination of the complete blood count (CBC), electrolytes, prothrombin time, and activated partial thromboplastin time, should be ordered. A search for the etiology of the symptoms should commence.

The level of globotriaosylceramide (Gb₃ or GL-3), a glycosphingolipid, may be elevated.

Enzymatic analysis performed by using plasma or leukocytes may show a deficiency of alpha-galactosidase A.

levels of Gb₃ and alpha-galactosidase A may be normal in female (heterozygote) Fabry patients. Therefore, genetic and/or molecular diagnosis is necessary to confirm Fabry disease if the disease is suspected based on clinical features of proteinuria and acroparesthesias that were invariably present in men and women with Fabry mutation and cryptogenic stroke. Men with Fabry mutation tend to have more clinical features when presenting with stroke.

Cardiomegaly may be readily evident on a chest radiograph.

Echocardiography may be indicated to investigate a possible source of emboli. Echocardiograms may reveal valvular abnormalities, ventricular hypertrophy, and flow abnormalities.

Brain MRI or computed tomography (CT) scans should be obtained to visualize the site and extent of infarction.

MR angiography (MRA), CT angiography (CTA), or 4-vessel cerebral angiography should be performed to identify large-vessel dilated arteriopathy, stenosis, or occlusion.

In patients with acute ischemic stroke, diffusion-weighted MRI may be used to identify early lesions, and perfusion-weighted MRI can be performed to identify perfusion defects.

MR spectroscopy, arterial spin tagged MR imaging, and positron emission tomography (PET) scanning have been performed on an experimental basis to understand the pathophysiology of Fabry disease.^[8]

A detailed neurologic examination may reveal peripheral neuropathy or nystagmus, internuclear ophthalmoplegia, dysarthria, aphasia, hemiparesis, and sensory loss caused by stroke lesions, especially in the posterior circulation.

Skin biopsy with cells showing increased lipid content is suggestive of Fabry disease.

Lipid-laden cells have been described in endothelial cells, epithelial cells, muscle fibers, and ganglion cells.

Electrocardiography may show conduction abnormalities and evidence of previous myocardial infarctions.

Nerve conduction studies may show decreased conduction velocities and prolonged distal latencies.

Prenatal diagnosis can be made by using samples of chorionic villi and amniotic cells.

Antiplatelet agents, including aspirin, ticlopidine, clopidogrel, and aspirin-dipyridamole, are used routinely to prevent recurrent ischemic strokes of thrombotic type in Fabry disease, but their effectiveness in this setting has not been proved.

Administration of the anticoagulant warfarin, which is often used to prevent cardioembolic strokes, may be necessary if embolic events that stem from cardiac causes are a concern.

Painful neuropathies may be treated with a variety of medications. Carbamazepine and phenytoin have been used anecdotally in Fabry disease.

Two enzymes, agalsidase-alpha (Replagal) and agalsidase-beta (Fabrazyme), reportedly help in normalizing renal function, cardiac function, and cerebrovascular flow. Whether therapy with these enzymes changes the natural history of strokes attributable to Fabry disease is unclear.

Medical regulatory requirements are different in various parts of the world, and the appropriate authorities should be consulted regarding the approval status of these enzymes.

Renal failure is a clear indication for renal transplantation. However, renal transplantation may not alter the course of disease progression in other organ systems.

Fetal liver transplantation has been tried in a small number of patients. In the limited group of patients tested, no changes in serum or leukocyte alpha-galactosidase A levels were reported. Clinical use of this experimental procedure should be undertaken with caution, since published literature on the topic is sparse.

Consultation with a neurologist is recommended if Fabry disease is suspected as a cause of stroke or if the usual causes of stroke are not present. In addition, a neurologist can better handle painful neuropathies that are not amenable to treatment in the primary care setting.

If an embolic event is thought to have caused a stroke, a cardiologist's expertise can be sought for diagnostic and therapeutic options.

A nephrologist should be consulted if a patient has renal failure.

Sessions with a physical therapist and an occupational therapist can be helpful in rehabilitative efforts.