A 50-year-old man with eruptive and palmar (planar) xanthomas has total cholesterol 340 mg/dL, triglycerides 500 mg/dL, and LDL 110 mg/dL. Lipoprotein electrophoresis shows a broad beta band. Homozygosity for which apolipoprotein variant is the classic cause?
- A Apolipoprotein A-I Milano
- B Apolipoprotein B-100 R3500Q mutation
- C Apolipoprotein E2/E2 ✓
- D Apolipoprotein C-II deficiency
Correct answer: C. Apolipoprotein E2/E2
Explanation
Familial dysbetalipoproteinemia (type III hyperlipoproteinemia) arises from homozygous apoE2, which binds hepatic LDL receptor and LRP poorly, causing impaired clearance of chylomicron remnants and IDL. It characteristically shows combined hypercholesterolemia and hypertriglyceridemia with normal LDL, broad beta band on electrophoresis, and pathognomonic palmar xanthomas. ApoB R3500Q causes familial defective apolipoprotein B-100 with isolated high LDL, ApoA-I Milano is protective, and apoC-II deficiency causes severe fasting chylomicronemia with low cholesterol.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.