Lipid Biochemistry USMLE Step 1 Practice Question
A 42-year-old man presents with orange discoloration of his palms and soles, eruptive xanthomas, and laboratory findings of total cholesterol 320 mg/dL, triglycerides 180 mg/dL, and elevated direct bilirubin. He is found to have a mutation in the gene encoding cholestanol 7α-hydroxylase. Which of the following represents the primary biochemical consequence?
Answer choices
- ADecreased hepatic VLDL synthesis due to reduced substrate availability
- BImpaired conversion of cholesterol to bile acids, causing cholestasis and lipid accumulationCorrect answer
- CIncreased LDL receptor expression due to intracellular cholesterol depletion
- DInhibition of intestinal lipid absorption via reduced bile acid secretion
- EPrimary defect in hepatic triglyceride synthesis
- FEnhanced conversion of cholesterol to oxysterols, leading to increased SREBP-2 activation
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