Homocystinuria refers to elevated excretion of the amino acid homocystine. In most cases this is a benign, temporary abnormality due to immature enzyme levels or a high protein intake. B 6 -responsive patients have been detected by urine screening at one month of age in some programs. Other signs and symptoms include intellectual impairment, seizures, arachnodactyly, joint stiffness, osteoporosis, fair skin and hair, liver damage, connective tissue damage, and psychiatric or emotional disorders.
Treatment is of variable efficacy.
Besides classic homocystinuria, several forms of hypermethioninemia are known. The condition may be benign or occur in association with mental retardation and myopathy. Deficiency of folic acid or vitamin B 12 causes methylmalonic acidemia with homocystinuria and metabolic disorders of B 12 formation produce the same biochemical sequelae but different symptoms. A bacterial inhibition assay for methionine is used for screening. Liver function tests are needed and a urine for succinylacetone may also be necessary to exclude tyrosinemia.