Lipid Biochemistry USMLE Step 1 Practice Question
A 38-year-old man presents with recurrent myocardial infarction despite atorvastatin 80 mg daily and normal LDL cholesterol of 95 mg/dL. Vital signs: BP 138/88 mmHg, HR 92 bpm, RR 16, temp 37°C, SpO2 98%. HDL cholesterol is markedly reduced at 28 mg/dL. Triglycerides are normal. Genetic testing reveals ABCA1 gene mutations. He denies smoking and alcohol use. Which mechanism best explains his accelerated atherosclerosis despite optimal LDL control?
Answer choices
- AReduced uptake of LDL particles by macrophage scavenger receptors
- BEnhanced oxidation of apolipoprotein B-100 in LDL particles
- CDecreased esterification of free cholesterol by LCAT
- DIncreased hepatic synthesis of apolipoprotein B-100
- EImpaired efflux of cellular cholesterol to apolipoprotein A-I, reducing HDL formationCorrect answer
- FImpaired conversion of VLDL remnants to LDL due to deficient hepatic lipase activity
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