Step 1

Biochemistry 2

A 3-year-old girl is brought to the emergency department by her parents for vomiting and lethargy for the past day and a new seizure one hour ago that lasted approximately 3 minutes. They report that she is taking amoxicillin for otitis media that was diagnosed two days ago. On physical examination, she is noted to have a fruity odor and has dry mucous membranes. A urine sample is obtained and is noted to have a distinct sweet-smelling odor. Laboratory results confirm a diagnosis of maple syrup urine disease (MSUD).

Which of the following amino acids is least likely to be elevated in this patient?

  • A) Cysteine
  • B) Isoleucine
  • C) Leucine
  • D) Valine


Dr. Ted O'Connell

Matthew Christensen


Dr. Ted O'Connell