[A mild variant case of maple syrup urine disease].

We reported a mild variant case of maple syrup urine disease. He was unable to walk alone at 2 years of age and developed seizures and intermittent ataxia at 5 years of age. Activity of 1-14C-leucine decarboxylase in fibroblasts revealed 40% of normal activity in the boy and 90% in the mother. MRI showed hypo-myelination of white matter and mild atrophy of brain stem and cerebellum. Dietary treatment was not effective for ataxia and brain atrophy.