Intraluminal fibrosis and elastic fiber degradation lead to lung remodeling in pulmonary Langerhans cell granulomatosis (histiocytosis X).

To evaluate the morphogenesis of lung remodeling in pulmonary Langerhans cell granulomatosis (LCG; previously called histiocytosis X or eosinophilic granuloma), lung tissues obtained by open biopsy from 62 patients with pulmonary LCG were studied by light and electron microscopy. Tissues from 20 patients were also studied by immunohistochemical methods for the detection of fibronectin, elastin, and S-100 protein, and samples from six patients were studied using OKT6 monoclonal antibody. In early stages of pulmonary LCG, the epithelial lining cells were detached and Langerhans cells, inflammatory cells, and myofibroblasts migrated into intraluminal spaces through gaps in the epithelial basement membranes in and around the granulomatous lesions. In late stages, intraluminal fibrosis led to obstruction of alveolar spaces and airways and to coalescence of alveolar walls in and around the granulomatous lesions. Adjacent to these lesions, irregularly dilated alveoli were found with degraded and disrupted elastic fibers. Together, these observations suggest that intraluminal fibrosis and elastic fiber degradation are important processes of lung remodeling in pulmonary LCG.