How is homocystinuria treated? What symptoms can be expected to respond?
Effective treatment requires early diagnosis to prevent mental retardation, which is the basis for newborn screening for inborn errors of metabolism. Vitamin B 6 and B 12 and folate are cofactors for the different enzymes involved in methionine metabolism. Half of patients respond to vitamin B 6 . Large doses of vitamin B 6 (300–600 mg/day of pyridoxine) lower blood methionine, raise blood cysteine, and improve symptoms in patients with cystathionine β-synthase deficiency, presumably by augmenting the small amount of residual enzyme activity. Development of ectopia lentis, osteoporosis, and retardation may be mitigated with therapy, but no remission of these conditions occurs if they are already present. Patients who do not respond to vitamin B 6 are treated with a low-protein, low-methionine diet with or without cysteine supplementation. Betaine, which converts homocysteine back to methionine, is also given to these patients.
