Methylene Tetrahydrofolate Reductase Deficiency.

5,10-Methylene-tetrahydrofolate reductase (MTHFR) deficiency is a rare, autosomal recessive, metabolic disorder of folate metabolism, which affects homocysteine remethylation. Elevated homocysteine with normal or low methionine level is the key to diagnosis. Early recognition and treatment with betaine, has been shown to improve the survival and neurological outcomes. The authors report five Indian patients from three unrelated families, with MTHFR deficiency to emphasize the importance of early recognition and initiation of specific treatment.