Titration of betaine therapy to optimize therapy in an infant with 5,10-methylenetetrahydrofolate reductase deficiency.

Betaine therapy was given for 2 years to a 2-year-old boy with 5,10-methylenetetrahydrofolate reductase deficiency. Used as a methyl donor to lower homocysteine levels through methylation of methionine, betaine has been reported to be effective in treating homocystinuria. Satisfactory biochemical and clinical responses were obtained with the following regimen: betaine started in the newborn period at increasing doses to reach 1 g given six times a day. It is suggested that frequent administration of a moderate dose may provide clinical and biochemical benefit.