Necrobiotic xanthogranuloma.

Necrobiotic xanthogranuloma (NXG) is an uncommon granulomatous disease involving the skin and extracutaneous tissues. In its typical clinical presentation, it consists of multiple indurate yellow-brownish plaques or nodules, usually located on the periorbital area. The lesions often are bilateral and symmetric and frequently show tendency to atrophy and ulceration. Most cases are asymptomatic, and oral mucosal erosions are sometimes present. Ophthalmologic complications are observed in many patients, and NXG may involve other extracutaneous sites. Paraproteinemia is closely associated with NXG, demonstrating a monoclonal gammapathy, and other hematologic or lymphoproliferative disorders also may appear in association with NXG. Large areas of degenerated collagen alternating with granulomatous inflammation, multinucleate giant cells, cholesterol clefts, and lymphoid follicles are the most outstanding histopathologic characteristics of NXG. The prognosis for NXG is good, but no curative treatment is available. Chemotherapy with alkylating agents is the most frequently administered treatment, but oral and intralesional corticosteroids, interferon alpha, plasmapheresis, surgical excision, and radiation therapy also have been used for treatment of this disorder, with variable results.