A 5-day-old female newborn, who is breast-fed, is brought to the ER because of a 2-day history of poor feeding and vomiting. Physical examination shows lethargy, dehydration, hypertonicity, and rigidity of the extremities. There is a sweet odor of maple syrup in the newborn's diaper. Laboratory studies show metabolic acidosis, ketosis, and hypoglycemia. Following treatment of this patient's acute condition, long-term therapy is begun. This therapy is most likely to restrict which of the following substances?

Question

Quizplus · Accepted Answer

The symptoms and sweet odor of the urine suggest Maple Syrup Urine Disease, which is caused by a defect in the metabolism of branched-chain amino acids: leucine, isoleucine, and valine. Long-term therapy involves dietary restriction of these amino acids.  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.

A 5-Day-Old Female Newborn, Who Is Breast-Fed, Is Brought to the ER