Necrobiotic xanthogranuloma-rapid progression under treatment with melphalan.

Necrobiotic xanthogranuloma is a systemic disease associated in most cases with monoclonal paraproteinaemia. Although the causative role of the paraproteinaemia is supposed, the pathogenesis of this disease remains unknown. We report a 65-year-old woman with a 28-year history of disseminated indurated plaques involving her face, trunk and extremities. Since 1994 an IgG kappa paraproteinaemia was present. Current biopsies showed typical histological features of necrobiotic xanthogranuloma. We treated this extraordinary widespread condition with melphalan and prednisolone. Although the serum levels of IgG kappa light chains and gamma globulins decreased, the cutaneous plaques extended rapidly in size and number, which casts doubt on the causative significance of the paraproteinaemia in the pathogenesis of necrobiotic xanthogranuloma. The paraproteinaemia in patients with necrobiotic xanthogranuloma may rather reflect a secondary phenomenon than the originating cause. Pathogenetic and therapeutical concepts based thereon that have been proposed so far should be critically reconsidered.