Pulmonary Langerhans' cell histiocytosis.

Pulmonary Langerhans' cell histiocytosis (PLCH) is an uncommon but important cause of interstitial lung disease, and it occurs predominantly in adult cigarette smokers. PLCH belongs to the spectrum of Langerhans' cell histiocytosis (LCH), diseases characterized by uncontrolled proliferation and infiltration of various organs by Langerhans' cells. Other clinical entities within this spectrum of LCH are seen in adults and children and vary in severity from mild disease that requires no therapy to severe disseminated forms with extensive organ involvement and high mortality. Organ systems involved by LCH may include skin, bone, pituitary gland, lymph nodes, and lungs. Although LCH is approximately three times more common in children than adults, pulmonary involvement is much more common in adults with LCH, in whom it frequently occurs as the sole organ involved with disease. This article summarizes recent advances and current understanding of PLCH.