[Histiocytosis X: historical review and therapeutic prospectives]

A number of factors should influence the choice of therapy in H.X. The three most important are: etiology, natural history and prognostic factors. At this time, we can identify 2 groups of patients: - the first is characterized by age greater than 2 years, bone involvement, absence of organ dysfunction, long survival, low mortality and high frequency of late effects (Good Risk Group); - the second group by age less than 2 years, soft tissue (+/- bone) involvement, presence of organ dysfunction and high mortality (Poor Risk Group). Chemotherapy appears to improve survival and Complete Remission rate in the Poor Risk Group but not in the Good Risk Group. New advances, i.e. immunotherapy, are in progress to reduce mortality in Poor Risk patients, late effects in Good Risk patients and related therapy sequelae.