Homocystinuria

Homocystinuria is a rare autosomal recessive disease caused by deficiency of cystathionine beta synthase. This results in an accumulation of homocysteine which is then oxidized to homocystine.

Features

• often patients have fine, fair hair
• musculoskeletal: may be similar to Marfan's - arachnodactyly etc
• neurological patients may have learning difficulties, seizures
• ocular: downwards (inferonasal) dislocation of lens
• increased risk of arterial and venous thromboembolism
• also malar flush, livedo reticularis

Diagnosis is made by the cyanide-nitroprusside test, which is also positive in cystinuria

Treatment is vitamin B6 (pyridoxine) supplements