A 42-year-old man has resistant hypercholesterolemia (total cholesterol 340 mg/dL), tuberoeruptive xanthomas over the elbows, and normal plasma triglycerides. Lipoprotein electrophoresis shows a broad beta band. Family screening reveals his homozygous sister has similar findings. Genotyping shows homozygosity for apolipoprotein E2. The defective process is:
- A LDL receptor mediated clearance of LDL
- B Hepatic recognition and uptake of chylomicron and VLDL remnants ✓
- C Lipoprotein lipase activation on capillary endothelium
- D LCAT-mediated esterification of free cholesterol on HDL
Correct answer: B. Hepatic recognition and uptake of chylomicron and VLDL remnants
Explanation
This is familial dysbetalipoproteinemia (type III hyperlipoproteinemia). ApoE2 binds defectively to the hepatic LDL receptor related protein and LDL receptors, impairing remnant clearance, so IDL-like beta-VLDL accumulates as a broad beta band. LDL receptors are intact, distinguishing it from familial hypercholesterolemia where triglycerides stay low and no broad beta band appears. LPL and LCAT are unrelated to remnant uptake.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.