[Necrobiotic xanthogranuloma in paraproteinemia].

Necrobiotic xanthogranuloma is a rare generalized dermatosis occurring exclusively in association with paraproteinemia. Clinically it is characterized by large, ulcerating, nodular and plaque-like tumors of the dermis and subcutis. Histologically the lesions are composed of a nonspecific, lymphocytic and plasmacellular infiltrate and highly characteristic granulomas with giant cells of the Touton and foreign body type. Ultrastructurally, tubular cystic organelles with a central lamella and a few ribosomes at their outer membranes are found. By means of histochemical studies we excluded the skin infiltrates as the site of the paraprotein release. The pathogenesis of the disease remains unclear; it is suggested that the paraprotein has functional features of a lipoprotein, which may bind to lipoprotein receptors of the histiocytes, thereby inducing xanthoma formation.