autosomal recessive inherited disorder with multiple forms of phenotypic expression, caused by a defect in the oxidative decarboxylation of branched-chain amino acids; metabolites accumulate in body fluids and render a "maple syrup" odor; divided into classic, intermediate, intermittent, and thiamine responsive subtypes; classic form presents in the first week of life with ketoacidosis, hypoglycemia, emesis, neonatal seizures, and hypertonia; the intermediate and intermittent forms present in childhood or later with acute episodes of ataxia and vomiting.