MAPLE syrup urine disease is a rare inborn error of branched-chain amino acid and branched-chain keto acid metabolism due to decreased branched-chain α-keto acid dehydrogenase-complex activity.¹ The branched-chain keto acids, which are the substrates in this irreversible enzyme reaction, are derived from transamination of the branched-chain amino acids leucine, isoleucine, and valine. Consumption of branched-chain amino acids in the form of dietary protein in excess of an age-dependent daily requirement for protein synthesis results in the accumulation of branched-chain amino acids and branched-chain keto acids in the tissues and body fluids of patients in whom there is little or no . . .