Necrobiotic xanthogranuloma.

Necrobiotic xanthogranuloma is a rare non-Langerhans histiocytosis often associated with paraproteinemia or hematologic disease. Necrobiotic xanthogranuloma is usually characterized by yellow-orange, reddish-brown, or violaceous papules and nodules that may progress to form infiltrative plaques, with lesions often occurring in a periorbital distribution. Histopathologic study typically demonstrates bands of inflammatory granulomatous tissue separated by zones of necrobiosis, with the dermis and subcutaneous tissue most commonly affected. Historically, diagnosis has been made based on consistent clinical and histologic findings, although diagnostic criteria have recently been proposed. Research on necrobiotic xanthogranuloma is limited due to the condition's rarity, making comparisons of therapeutic agents difficult. Numerous systemic and localized treatments have been documented, with varying responses.