Lipid Biochemistry USMLE Step 1 Practice Question
A 28-year-old woman with severe hypertriglyceridemia (890 mg/dL) reports yellowing of her palms and severe abdominal pain. She is not pregnant and denies alcohol use. Genetic testing reveals a heterozygous mutation in the apoC-II gene. Which of the following best explains why she has symptomatic disease despite heterozygous carrier status?
Answer choices
- ASecondary deficiency of apoA-I reducing HDL-mediated cholesterol efflux
- BDominant-negative effect of the mutant apoC-II protein competing with wild-type protein
- CX-linked inheritance pattern resulting in complete absence of apoC-II in females
- DHaploinsufficiency: one functional apoC-II allele is insufficient to generate adequate cofactor for lipoprotein lipaseCorrect answer
- EAccumulation of toxic cholesterol esters in the pancreas
- FLoss-of-function mutation in the APOC2 regulatory region preventing compensatory upregulation of the remaining functional allele
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