Metabolism USMLE Step 1 Practice Question
A 31-year-old woman presents with recurrent jaundice during pregnancy (BP 118/76, HR 82, RR 16, Temp 37°C, SpO2 98%). Laboratory studies reveal elevated direct bilirubin at 3.2 mg/dL with normal AST/ALT (<40 U/L). Abdominal ultrasound shows no gallstones or biliary obstruction. Liver biopsy demonstrates dark brown pigmentation within hepatocytes. She denies pruritus or acholic stools. Which enzyme defect best explains these findings?
Answer choices
- AAutoimmune destruction of intrahepatic bile ducts
- BImpaired bilirubin conjugation in hepatocytes
- CDeficiency of glucose 6 phosphate dehydrogenase
- DExcess heme breakdown due to occult hemolysis
- EDefective canalicular secretion of conjugated bilirubinCorrect answer
- FReduced hepatic uptake of unconjugated bilirubin from sinusoids
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