Deficiency, alpha-galactosidase A

Fabry disease, a genetic disorder. The enzyme alpha-galactosidase A is essential to the metabolism of molecules known as glycosphingolipids. Without the enzyme, glycosphingolipids accumulate in the kidneys, heart, nerves and throughout the body, causing Fabry disease. Males with Fabry disease are more severely affected than females since the gene for Fabry disease is on the X chromosome. Males have only one X while females have a second X and therefore some enzyme activity. Boys with Fabry disease usually have discomfort of the hands and feet with abnormal sensation (paresthesia) or burning pain by adolescence. Red raised lesions known as angiokeratomas occur on the skin and within the mouth. The ability to sweat is decreased. The cornea and lens of the eye become clouded. There may be painful abdominal crises. Renal impairment may require dialysis or kidney transplant. The kidney failure may cause hypertension. Heart function can be impaired. Females with partial enzyme activity may not show any symptoms or only late in life. Impaired heart function may be their primary problem. Diagnosis is made by determining the level of alpha-galactosidase A in blood plasma or by genetic testing to detect the abnormal gene. Treatment is by enzyme replacement. Twice weekly infusions of recombinant galactosidase A have been found to be safe and effective in clearing deposits from the kidney blood vessels, myocardium (heart muscle), and skin. In August 2001 the European Union granted orphan drug status to two forms of recombinant galactosidase A — Replagal (agalsidase alfa) and Fabrazyme (agalsidase beta) — for long-term enzyme replacement in Fabry disease. In Europe, orphan drug status means no third party can compete with them for 10 years. Neither Replagal nor Fabrazyme had received approval in the United States.