Lymphomatoid papulosis.

Lymphomatoid papulosis is an unusual chronic skin disease characterized by the continuous appearance of papulonecrotic, nodular, and occasionally larger tumorous or plaque-like lesions showing histologic features suggestive of malignant lymphoma. The recognition of two histologic types of lymphomatoid papulosis, which are not distinct entities but represent the ends of a spectrum, has provided an explanation for the clinical and histologic variation and many of the current controversies in this disorder. These two types of lymphomatoid papulosis, called type A (or "histiocytic" type) and type B (or lymphocytic type), have been shown to be related to Hodgkin's disease and mycosis fungoides, respectively. Current evidence suggests that these conditions result from abnormal immune reactions to persistent and as yet unidentified antigens. This concept does not resolve the question of whether lymphomatoid papulosis is an inflammatory or malignant disease. In most patients, lymphomatoid papulosis runs a protracted but benign course. In others, however, it is associated with or develops into malignant lymphoma. Because reliable clinical and histologic criteria predictive of such a transition are lacking, all patients with lymphomatoid papulosis require close long-term follow-up.