[Case of juvenile stroke caused by methylenetetrahydrofolate reductase deficiency].

The patient had suffered from left hemiparesis at the age of thirteen months, and acute ischemic stroke of unknown etiology had been diagnosed at that time. His hemiparesis gradually disappeared and he was discharged two weeks after the onset without disability. At the age of 17 years, MRI following minor head trauma revealed cerebral infarctions located at the right corona radiata and basal ganglia. Laboratory findings showed hyperhomocysteinemia. Genetic study disclosed methylenetetrahydrofolate reductase deficiency (MTHFRD) (valine/valine type). MTHFRD is not detected by the routine infantile mass screening test for congenital amino acid metabolic disease, and should be considered in any patient with ischemic stroke at under two years of age.