A 19-year-old boy with newly diagnosed uncontrolled type 1 diabetes presents with a sudden crop of firm, dome-shaped, erythematous papules with a subtle yellow hue over the buttocks and extensor surfaces of the thighs. Serum triglycerides are markedly elevated. What is the expected histology?
- A Lipid-laden foamy macrophages within the dermis ✓
- B Palisading granulomas around altered collagen
- C Subepidermal vesicle with festooning of dermal papillae
- D Dense neutrophilic infiltrate in the upper dermis
Correct answer: A. Lipid-laden foamy macrophages within the dermis
Explanation
Eruptive xanthomatosis develops when chylomicron levels rise sharply, classically with serum triglycerides above 1000 to 2000 mg/dL in uncontrolled diabetes; biopsy shows clusters of lipid-filled foamy histiocytes in the dermis. Palisading granulomas point to granuloma annulare or necrobiosis lipoidica, and festooning of papillary dermis is seen in porphyria cutanea tarda, neither of which fits this presentation.
Reference: Bolognia, Dermatology, 5th ed.
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