Lipid Biochemistry USMLE Step 1 Practice Question
A 19-year-old female with consanguineous parents presents with orbital and eruptive xanthomas on the buttocks. Vital signs: BP 118/76, HR 88, RR 16, Temp 37°C, SpO2 98%. Serum triglycerides are 1,200 mg/dL; lipase is normal. She denies abdominal pain. Genetic testing reveals homozygous loss-of-function mutations in the APOC2 gene. Which mechanism best explains persistently elevated triglycerides despite normal hepatic lipase activity?
Answer choices
- AImpaired hepatic synthesis of apolipoprotein B-48 from enterocytes
- BIncreased clearance of chylomicrons via hepatic apoE receptors
- CAbsence of apoC-II cofactor prevents lipoprotein lipase activation at the capillary endotheliumCorrect answer
- DReduced activity of lecithin-cholesterol acyltransferase in circulation
- EEnhanced VLDL particle production by the liver
- FDefective apoC-III synthesis leading to impaired inhibition of hepatic triglyceride lipase
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