This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolic disorders, Subject name: Pediatrics
Deficiency of enzyme a-keto acid decarboxylase leading to a block in the metabolism of branch chain amino acids is observed in 
Select and explain. 
A. Maple syrup urine disease, B. Hanup's disease, C. Alkaptonuria, D. Phenylketonuria
A: Maple syrup urine disease
Answer: A: Maple syrup urine disease 
Explanation: Maple syrup urine disease(MSUD) is due to increased activity of branched chain alpha ketoacid dehydrogenase(BCKAD) complex,a mitochondrial enzyme involved in degradation of branched chain amino acids(leucine,isoleucine, and valine).This enzyme has 4 subunits:E1alpha,E1beta,E2 and E3. Reference:Essential pediatrics-Ghai,8th edition,page no:652