Treatment of homocystinuria with pyridoxine. A preliminary study.

Homocystinuria is the result of an inborn error in the metabolism of the essential sulphur-containing amino acid, methionine (Carson and Neill, 1962; Gerritsen, Vaughn, and Waisman, 1962). There is now good evidence This results in an accumulation of homo- cysteine in the blood, and as this is a 'non-threshold' amino acid, it is rapidly excreted in the urine in its oxidized form, homocystine. Homocysteine may be remethylated to methionine with the aid ofmethyl group donors such as N5-methyltetrahydrofolic acid (M5FH4) or betaine; the accumulation of homocysteine favours remethylation, and results in raised serum methionine levels. As cysteine cannot be formed, it now becomes an essential amino acid, and the patient depends on the dietary intake for his cysteine requirements. There…