Necrobiotic Xanthogranuloma (NXG)

Figure 3.15 A: Necrobiosis lipoidica (Courtesy of Dr. Sophie M. Worobec) B: Necrobiosis lipoidica (Courtesy of Dr. Paul Getz) C: Necrobiotic xanthogranuloma (Reprint from Morgan MB, Smoller BR, Somach SC. Deadly Dermatologic Diseases . New York, NY: Springer; 2007)

• Rare, multisystem histiocytic disease
• Presents as red-orange to yellow papules, nodules or plaques on face (periorbital), tendency toward ulceration
• 80% with IgG monoclonal gammopathy (↑ risk of plasma cell dyscrasias and lymphoproliferative disorders)
• Histology: mid-dermal palisading xanthogranuloma with areas of necrobiotic, degenerated collagen that infiltrates the mid-dermis with extension into the subcutaneous fat; foamy histiocytes, plasma cells, giant cells (Touton and bizarre foreign body), and cholesterol clefts within granulomas