Lipid Biochemistry USMLE Step 1 Practice Question
A 45-year-old man with premature coronary artery disease (diagnosed at age 42) presents with yellow nodules on his elbows and Achilles tendons, plus corneal arcus. Vital signs: BP 148/92 mmHg, HR 88/min, RR 14/min, temp 37°C. Laboratory studies reveal LDL cholesterol 520 mg/dL, triglycerides 95 mg/dL (normal), and HDL cholesterol 38 mg/dL. Coronary angiography confirms significant stenosis. Which genetic defect best explains his phenotype?
Answer choices
- ALoss-of-function mutation in LDL receptor geneCorrect answer
- BGain-of-function mutation in PCSK9
- CDeficiency of lipoprotein lipase
- DMutation in cholesterol 7-alpha-hydroxylase
- EDeficiency of apolipoprotein B-100
- FLoss-of-function mutation in LCAT gene
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