<prompt> An infant presents to OPD with a history of vomiting and poor feeding. The burnt sugar odor is present in babys urine. Lab examination reveals elevated levels of leucine, isoleucine and valine. The most likely diagnosis is ?PhenylketonuriaAlkaptonuriaTyrosinemiaMaple syrup urine disease  <response>: The odor of urine in maple syrup urine disease branched-chain ketonuria, or MSUD suggests maple syrup or burnt sugar.The biochemical defect in MSUD involves the α-keto acid decarboxylase complex. Plasma and urinary levels of leucine, isoleucine, valine and their α-keto acids and α-hydroxy acids reduced α-keto acids are elevated, but the urinary keto acids derive principally from leucine. Signs and symptoms of MSUD include often fatal ketoacidosis, neurological derangements, mental retardation, and a maple syrup odor of urine. The mechanism of toxicity is unknown. Early diagnosis by enzymatic analysis is essential to avoid brain damage and early mortality by replacing dietary protein by an amino acid mixture that lacks leucine, isoleucine, and valine.Reference- Harpers illustrated biochemistry. 30th edition page -304 