[Prognostic factors in histiocytosis X].

Evaluation of prognostic factors and therapeutic strategies in histiocytosis X is difficult because of this disease's low incidence, heterogeneity related to the multiplicity of possible localizations, unpredictable course, and incompletely elucidated pathogenesis. At the time of diagnosis, parameters with a bearing on prognosis include age, number of involved organs, presence or absence of organ dysfunction, and initial response to treatment. Chemotherapy regimens, of which the most effective are vinblastine-corticosteroids and etoposide-corticosteroids, should be used only in patients with organ dysfunction or involvement of two or more organs before two years of age or three or more organs after two years of age. Duration of treatment ranges from three to twelve months according to the quality of the response. Other treatments, including low dose cytosine, alpha-interferon, or even autologous or allogeneic bone marrow transplantation have yielded promising results that need to be confirmed in a larger number of patients.