A 1-week-old neonate presents with poor feeding, vomiting, and progressive lethargy progressing to seizures and opisthotonus. The infant's urine has a distinctive sweet, burnt maple syrup odor. Blood analysis shows markedly elevated branched-chain amino acids. Which enzyme deficiency is responsible for this condition?

• A Branched-chain alpha-ketoacid dehydrogenase ✓
• B Phenylalanine hydroxylase
• C Galactose-1-phosphate uridylyltransferase
• D Homogentisate oxidase

Explanation

Maple syrup urine disease is caused by a deficiency of the branched-chain alpha-ketoacid dehydrogenase complex. This enzyme normally metabolizes leucine, isoleucine, and valine. Their accumulation and subsequent ketoacid production cause neurotoxicity and the characteristic maple syrup odor. Phenylalanine hydroxylase deficiency causes phenylketonuria, galactose-1-phosphate uridylyltransferase deficiency causes galactosemia, and homogentisate oxidase deficiency causes alkaptonuria.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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