Histiocytic syndromes: a review.

Histiocytoses represent a large, puzzling group of rare skin diseases. The purpose of this review is to schematically outline the clinical, histologic, and ultrastructural features of the most important histiocytic syndromes and to provide the pertinent differential diagnoses. For convenience, we have followed the criterion suggested by Winkelmann, distinguishing these conditions into X and non-X. Among the non-X histiocytoses the self-healing forms have been treated first; the progressive forms follow.