Necrobiotic xanthogranuloma with paraproteinemia; an atypical case

Necrobiotic xanthogranuloma (NXG) is a rare marker for paraproteinemia. An 86-year-old woman had a one year history of large red-yellow to brown annular plaques involving all limbs. Biopsies showed a non-palisading granuloma with numerous multinucleated giant cells showing prominent elastophagocytosis and extensive areas of necrobiosis throughout the entire dermis. Complete loss of elastic fibers was observed in the central atrophic area of an annular plaque. Small vascular thromboses were also present. Laboratory findings revealed paraproteinemia of IgG-lambda type. Immunohistochemical staining detected the presence of roughly equal numbers of IgG-lambda-and IgG-kappa-staining plasma cells in the dermis. We diagnosed NXG with paraproteinemia with monoclonal gammopathy (IgG-lambda type) of unknown significance.