Introduction & Objective: Pulmonary Langerhans Cell Histiocytosis (PLCH) is an uncommon (5% ILD) interstitial tissue disorder with significant importance. It occurs predominantly in adult smokers. The organs involved in LCH include skin, bone, pituitary gland, thyroid, lymph node, and lungs.

Materials & Methods: In this descriptive study all patients admitted to the Masih Daneshvari Hospital in Tehran from 1996 to 2007 diagnosed with LCH (recognized by clinical features, laboratory investigations, radiological manifestations, BAL and biopsy) were evaluated. Results: A total of 20 patients were studied mean age was 27.8 yrs. 40% were smokers 80% had pulmonary involvement while in 20% other organs were affected. On spirometry, a mixed pattern (50%) was the most common and on chest radiography (CXR) 77% of lung cysts were visible. The most frequent finding on CT- scan was diffuse lung cysts (80%).

Conclusion: It is notable that ground glass opacity and consolidation occur in the early stages of disease. Since most of the patients refer with features of advanced disease, it is essential for the physicians to consider the early signs during the diagnostic stage. Also bronchoscopy and bronchial lavage are recommended in selected cases.