CNS Nutrition Specialist Exam Prep

Answer: D - Maple-syrup urine disease (MSUD) in an autosomal recessive disorder in infants caused by the inability of the body to metabolize the branched-chain amino acids leucine, isoleucine, and valine. The inability to break down branched-chain amino acids is due to a mutation in the gene that controls the activity of the enzyme alpha-keto acid dehyrogenase. Plasma levels of leucine exceeding 10 mg/dl are associated with the symptoms of MSUD, including lethargy, vomiting, and neurologic changes.