[Cutaneous histiocytosis X].

Histiocytosis X comprises three clinical entities whose common substrate is a localized or systemic proliferation of atypical histiocytes. On the basis of the age of manifestation, acuity of the clinical course and organ involvement Abt-Letterer-Siwe's disease, Hand-Schüller-Christian's disease and eosinophilic granuloma can be differentiated from each other, although transitional varieties of these syndromes are possible. Not infrequently oligosymptomatic forms are misinterpreted, especially when the skin is the only involved organ. In the following case report cutaneous histiocytosis X will be discussed in terms of its clinical expression. Electron-microscopy has proved to be the best methods to make the diagnosis of such atypical cases.