Pulmonary Langerhans cell histiocytosis: A case series and literature review.

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare diffuse parenchymal lung disease representing 3% of all interstitial lung diseases. PLCH occurs either as part of multi-system Langerhans cell histiocytosis (LCH) or an isolated disease of the lung. Isolated involvement of lungs is observed in approximately 50-70% of LCH cases and the age of onset peaks between 20 and 40 years without gender difference. Cigarette smoking is the only identified environmental risk factor. PLCH is characterized by Langerhans cell infiltrates that in general are in a bronchiolocentric distribution. Pulmonary lesions can occur after chronic systemic disease or are an initial sign of disease. The aims of this study are to (1) report five rare cases of PLCH in adults; (2) discuss the relationship of PLCH with interstitial lung fibrosis; (3) provide a concise review of PLCH epidemiology, pathophysiology, diagnosis, treatment, and prognosis to improve the knowledge of PLCH by pneumologists and internal medicine physicians.