Pulmonary Langerhans' cell granulomatosis (LCG).

Pulmonary Langerhans' granulomatosis (LCG) is characterised by infiltration of peripheral airways by dendritic cell precursors and Langerhans' cells (LC) together with eosinophils and mixed chronic inflammatory cells. Consequent airways destruction commonly leads to cystic changes and frequent pneumothorax. LC's are best identified by the electron microscope finding of Birbeck granules. Immunocytochemical markers are also of value. They are frequent in the early stages though absent in end stage disease. LCG is distinguished from sarcoidosis by the absence of epithelioid cell granulomas, association with heavy cigarette smoking in young males and frequency of pneumothorax. Both diseases show lymphocytosis in bronchoalveolar lavage but differ in that LCG shows a predominance of T-suppressor cells and sarcoidosis an excess of T-helper cells.