An 11-month-old boy is brought to the physician because of lethargy and irritability for the past 3 days, since a diagnosis of a middle ear infection. The physician prescribed an antibiotic to treat the ear infection. Laboratory studies show metabolic acidosis and an increased plasma valine concentration. Which of the following amino acid concentrations are most likely to be increased in this patient's blood if he has maple syrup urine disease?

Question

Quizplus · Accepted Answer

Maple syrup urine disease is characterized by an inability to break down branched-chain amino acids, leading to increased levels of leucine, isoleucine, and valine in the blood. Maple syrup urine disease (MSUD), also called branched-chain aminoaciduria, is so called because the urine of affected individuals smells like maple syrup or burnt sugar. MSUD results from a deficiency in an enzyme, branched-chain a-keto acid dehydrogenase (BCKD), that is involved in the catabolism of the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine.

An 11-Month-Old Boy Is Brought to the Physician Because of Lethargy