Pulmonary Langerhans cell granulomatosis.
Pulmonary Langerhans cell granulomatosis (LCG), also called histiocytosis X, is characterized by the presence of destructive granulomas containing large numbers of Langerhans cells. The lesions are almost exclusively centered on distal bronchioles, and it may be more accurate to consider the disease as a bronchiolitis. Isolated pulmonary LCG is an uncommon disease that usually affects young adult smokers. Multifocal or diffuse involvement can also occur, though more often in infants or children. High-resolution computed tomography has proved to be useful in the diagnosis of the disease by allowing the identification of characteristic cystic lesions associated with nodules. Bronchoalveolar lavage strongly supports the diagnosis in only the occasional patient. The pathogenesis of pulmonary LCG remains unknown, although several arguments suggest that, at least in adults, it may result from an uncontrolled immune response initiated by Langerhans cells. Granulocyte macrophage colony-stimulating factor could be one of the factors responsible for the local accumulation of Langerhans cells in early lesions. Recently, evidence that lesional Langerhans cells are of clonal origin has been reported in patients who have various forms of the disease, but this finding has not yet been shown for pulmonary LCG. Further studies are needed to determine whether the pathogenetic mechanisms are different in patients who have localized or diffuse forms of the disease.
Soler
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P
Institut National de la Santé et de la Recherche Médicale, Paris, France.
Tazi
A
A
Hance
A J
AJ
D000328:Adult; D006646:Histiocytosis, Langerhans-Cell / Q000473:pathology*; D006801:Humans