Pathophysiology
Clinical meaning
Pulmonary Langerhans cell histiocytosis (PLCH) is characterized by clonal proliferation of Langerhans cells (specialized dendritic cells bearing CD1a and CD207/langerin markers) that infiltrate the small airways and interstitium. Cigarette smoke antigens are believed to trigger this abnormal immune response. The Langerhans cells form peribronchiolar granulomas that destroy airway walls and adjacent alveoli. Early lesions are cellular and inflammatory; mature lesions become fibrotic and form stellate scars. End-stage disease features cystic destruction of lung parenchyma and can lead to pulmonary hypertension.