[Adult pulmonary Langerhans cell histiocytosis]

There is a strong relationship between tobacco smoking and pulmonary Langerhans cell histiocytosis (LCH) in adults. Definitive diagnosis relies on lung histology. In certain cases, the diagnosis can be retained on a typical nodulo-cystic pattern on lung high-resolution computed tomography (HRCT) and appropriate clinical setting. The main differential diagnoses to consider vary according to nodulo-cystic or only cystic pattern on lung HRCT and the clinical context. The natural history of the disease is better known and regular evaluation of respiratory function is essential during the follow-up of the patients. The disease may regress or remain stable and mild without treatment in a significant number of cases. Smoking cessation is the essential first step because it reduces the risk of early disease progression. Cladribine is the only treatment that has shown improvement in respiratory function. Its efficacy and tolerance will be clarified in the near future. Therapies targeting mutations in the MAPK pathway represent new therapeutic options that need to be appropriately evaluated pulmonary LCH.