[Langerhans cell histiocytosis]

We describe the case of male diagnosed with histiocytosis of Langerhans cells. Histiocytosis X is an interstitial disease with a real incidence and an unknown prevalence that can be suspected due to epidemiological and radiological data. The diagnosis can be realized using BAL and/or anatomo-pathological study of a biopsy. The principal treatment is to give up the tobacco habit. Evolution can be favourable.