Random Dermatology MCQ - Type III dysbetalipoproteinemia

A 55-year-old fisherman presents with asymptomatic, waxy, yellow-orange papules coalescing into plaques on his neck and axillae. The lesions appear stuck-on and show a positive folded ear sign. A skin biopsy reveals dermal deposition of lipid-laden macrophages. Which of the following is the most likely underlying metabolic abnormality?

A) Type I hyperlipoproteinemia
B) Type IIa hypercholesterolemia
C) Type III dysbetalipoproteinemia
D) Type IV hypertriglyceridemia
E) Type V mixed hyperlipidemia

Correct Answer: C) Type III dysbetalipoproteinemia

Explanation

Key Features of Eruptive Xanthomas in Type III Dysbetalipoproteinemia:

1. Clinical Presentation:

   • Tuberoeruptive xanthomas: Yellow-orange papules/plaques on extensor surfaces (elbows, knees) and intertriginous areas.

   • "Folded ear" sign: Xanthomatous infiltration of the anthelix (pathognomonic for type III).

   • Palmar xanthomas: Orange-yellow streaks in palmar creases.

2. Histopathology:

   • Foamy macrophages in the dermis with lipid deposition.

   • Perivascular inflammation may be present.

3. Metabolic Defect:

   • Defective ApoE2 clearance of chylomicron/VLDL remnants → elevated IDL.

   • Lab findings: ↑↑ cholesterol + triglycerides, "broad beta band" on lipoprotein electrophoresis.

Why Not Other Options?

• (A) Type I: Eruptive xanthomas (trunk/buttocks) + lipemia retinalis (LPL deficiency).

• (B) Type IIa: Tendon xanthomas (Achilles/extensors), normal triglycerides.

• (D) Type IV: Eruptive xanthomas (high TG only), no folded ear sign.

• (E) Type V: Mixed eruptive + tuberous xanthomas, no palmar involvement.

Management:

• First-line: Fibrates (gemfibrozil) to reduce IDL.

• Statin adjunct: If LDL remains elevated.

• Dietary: Low-fat, reduced alcohol.

Prognosis: High risk for premature atherosclerosis if untreated.