Maple Syrup Urine Disease

Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder affecting branched-chain amino acid (BCAA) metabolism. The condition results from deficiency in the branched-chain alpha-ketoacid dehydrogenase complex, an essential enzyme for catabolizing leucine, isoleucine, and valine. In the classical form, toxic accumulation of these amino acids and their metabolites begins within days of birth, causing severe metabolic acidosis, cerebral edema, seizures, and permanent neurological damage or death if untreated. The characteristic maple syrup or burnt sugar odor in urine and sweat is a diagnostic clue. Newborn screening has been transformative for MSUD management, allowing early detection and intervention before symptomatic illness develops. Lifelong management involves a specialized diet restricted in branched-chain amino acids, supplemented with medical foods containing balanced non-BCAA amino acids. Strict diet adherence during infancy and childhood is critical for preventing intellectual disability and neurological complications.