Homocystinuria

Homocystinuria is an inherited disorder of the metabolism of the amino acid methionine, caused by a deficiency of the enzyme cystathionine beta synthase or of methionine synthase. It follows an autosomal recessive pattern, so a child must inherit a faulty copy of the gene from each parent. Homocysteine builds up in the blood and is passed in excess in the urine, producing a multi-system disorder that affects the connective tissue, muscles, central nervous system and cardiovascular system. Infants usually look normal and early signs are vague. Similar findings can arise from deficiency of vitamin B6, vitamin B12 or folate. Many patients are treated with high doses of vitamin B6, and others respond to folic acid and betaine together with a low-methionine diet. Untreated, a large share of patients die of thrombotic complications before the age of thirty.