Fabry's disease

Overview
Fabry disease (also known as Anderson-Fabry disease, Angiokeratoma corporis diffusum, Ceramide trihexosidosis, and Sweeley-Klionsky disease) is an X-linked recessive inherited lysosomal storage disease.

Pathophysiology
A deficiency of the enzyme alpha galactosidase A causes a glycolipid known as globotriaosylceramide (also abbreviated as Gb3, GL-3, or ceramide trihexoside) to accumulate within the blood vessels, other tissues, and organs. This accumulation leads to an impairment of their proper function. The condition affects hemizygous males, as well as both heterozygous and homozygous females; males tend to experience the most severe clinical symptoms, while females vary from virtually no symptoms to those as serious as males. This variability is thought to be due to X-inactivation patterns during embryonic development of the female.

Symptoms
Symptoms include anhidrosis, fatigue, and red spots on skin. Some of the most common pathological symptoms includes skin lesions (angiokeratomas), and a burning pain of the extremities. This pain can become very intense, especially when one has a fever. Angiokeratomas are tiny, painless papules that appear at any region of the body, but are predominant on the thighs, buttocks, lower abdomen, and groin. Ocular involvement may be present showing cornea verticillata (also known as vortex keratopathy); this corneal whorling does not have any effect on vision or eye function. Symptoms are typically first experienced in early childhood and can be very difficult to understand; the rarity of Fabry disease to many clinicians sometimes leads to misdiagnoses or ignorance. Manifestations of the disease usually increase in number and severity as an individual ages.

Kidney complications are a common and serious effect of the disease; renal insufficiency and renal failure may worsen throughout life. Proteinuria is often the first sign of kidney involvement. Cardiac complications occur when Gb3 builds up in different heart cells; heart related effects worsen with age and may lead to increased risk of heart disease. Cerebrovascular effects lead to an increased risk of stroke. Other symptoms include an inability or decreased ability to sweat, fatigue, ringing in the ears (tinnitus), vertigo, nausea, and diarrhea.

Fabry's disease may also have ocular involvement, such as the presence of corneal verticillata in the basal layers of the epithelium, conjunctival aneursyms, and spokelike cataracts. Papilledema, macular edema, optic atrophy and retinal vascular dilation may also be present.

Treatment
Until recently, treatment of Fabry disease targeted the symptomatic effects. However, it is currently being treated at the cellular level through enzyme replacement therapy using Agalsidase alpha (Replagal) and Agalsidase beta (Fabrazyme®). The cost of these drugs is problematic (approximately $170,000 US a year/patient) and remains a barrier to many patients in some countries. Enzyme replacement therapy (typically infused every two weeks) may be performed in the patient's home by the patients themselves. Enzyme replacement therapy is not a cure, and must be infused recurrently for maximum benefit.

Eponym

 * It is named for Johannes Fabry.