This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': "An infant presents to OPD with a history of vomiting and poor feeding.\xa0The burnt sugar odor is present in baby's urine. Lab examination reveals elevated levels of leucine,\xa0 isoleucine and valine. The most likely diagnosis is ? \nSelect and explain. \nA. Phenylketonuria, B. Alkaptonuria, C. Tyrosinemia, D. Maple syrup urine disease", 'role': 'user'}, {'content': 'Answer: D \nExplanation: The\xa0odor\xa0of\xa0urine\xa0in\xa0maple\xa0syrup urine disease (branched-chain ketonuria, or MSUD) suggests maple syrup\xa0or burnt sugar.\nThe biochemical defect in\xa0MSUD\xa0 involves\xa0the\xa0α-keto\xa0acid\xa0decarboxylase\xa0complex. Plasma and urinary levels of\xa0 leucine,\xa0isoleucine,\xa0valine\xa0and\xa0their\xa0α-keto\xa0acids\xa0and 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\xa0diagnosis by enzymatic analysis is essential to avoid brain damage and early mortality by replacing dietary protein by an\xa0amino\xa0acid\xa0mixture\xa0that\xa0lacks\xa0 leucine,\xa0isoleucine,\xa0and valine.\nReference- Harper’s illustrated biochemistry. 30th edition page -304', 'role': 'assistant'}]