Lipid Biochemistry USMLE Step 1 Practice Question
A 45-year-old man presents with xanthomas on his Achilles tendons and eyelids, along with premature coronary artery disease at age 42. Serum LDL cholesterol is 520 mg/dL despite a low-fat diet. Genetic testing confirms a mutation in the LDL receptor gene. Which of the following best explains the pathophysiology of his lipid abnormality?
Answer choices
- AExcessive hepatic cholesterol synthesis from increased acetyl-CoA carboxylase activity
- BImpaired apolipoprotein B synthesis leading to accumulation of cholesterol
- CDecreased hepatic uptake of LDL particles due to absent or non-functional LDL receptorsCorrect answer
- DIncreased secretion of VLDL from hepatocytes secondary to elevated triglycerides
- EDeficiency of lipoprotein lipase preventing chylomicron clearance
- FImpaired conversion of VLDL to IDL due to hepatic lipase deficiency
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