Practice sessionHealth SciencesMEDICAL LICENSING
USMLE (United States Medical Licensing Examination) Practice Exam 07
Practice exam for USMLE (United States Medical Licensing Examination).
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Question 1 of 1000%
Time remaining120:00
Attempts allowedUnlimited
Difficulty mixE • M • H
Question 1
MEDIUMA 5-day-old newborn develops vomiting, poor feeding, and lethargy. Physical exam shows hypotonia. Labs show an elevated anion gap metabolic acidosis and markedly increased serum ammonia. Urine organic acid analysis reveals elevated methylmalonic acid. Which enzyme is most likely deficient?
Methylmalonic acidemia is due to methylmalonyl-CoA mutase deficiency (or B12 deficiency), causing metabolic acidosis and hyperammonemia in neonates.
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