A mother has brought her 3-month-old baby to the pediatrician and indicates that the infant is lethargic and has poor suckling and seems uninterested in eating. In addition, the mother notes that the baby's diapers often smell like burnt sugar. This infant likely has a defect in which of the following enzymes?

Question

Quizplus · Accepted Answer

The symptoms described, including lethargy, poor feeding, and the characteristic burnt sugar smell of the diapers, are indicative of Maple Syrup Urine Disease, which is caused by a defect in the branched-chain α-keto acid dehydrogenase enzyme. The symptoms exhibited by the infant are reflective of maple syrup urine disease (MSUD). This disease is caused by defects in branched-chain a-keto acid dehydrogenase, one of the enzymes used in the catabolism of the branched-chain amino acids (BCAAs) and the associated branched-chain a-keto acids (BCKAs). The classical symptom of this disease is the odor of burnt sugar in the diapers of afflicted infants. Left untreated, infants will die in the first few months of life from recurrent metabolic crisis and neurologic deterioration.

A Mother Has Brought Her 3-Month-Old Baby to the Pediatrician