Metabolism USMLE Step 1 Practice Question
A full-term newborn presents with severe jaundice within 12 hours of life. Vital signs show HR 160/min, RR 48/min, temperature 37.2°C. Total bilirubin is 28 mg/dL (predominantly unconjugated); direct bilirubin is 0.8 mg/dL. Peripheral blood smear shows no evidence of hemolysis. The infant is lethargic with high-pitched crying and mild hypertonia. Mother reports no medications during pregnancy. Which inherited metabolic defect most likely explains these findings?
Answer choices
- ADefective multidrug resistance associated protein 2 canalicular transporter
- BDeficiency of biliverdin reductase
- CDeficiency of heme oxygenase
- DPartial deficiency of bilirubin UDP glucuronosyltransferase
- EAbsent bilirubin UDP glucuronosyltransferaseCorrect answer
- FDeficiency of lipoic acid synthase
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.