Histiocytose langerhansienne pulmonaire de l'adulte

Abstract

Adult pulmonary Langerhans cell histiocytosis (LCH), is a rare disorder of unknown etiology which occurs predominantly in young smokers, with a peak incidence between 20 and 40 years of age. In adults, pulmonary involvement with LCH is usually an isolated manifestation and is characterised by Langerhans cells (CL) granulomas infiltrating and destroying the wall of distal bronchioles. High resolution chest tomography (HRCT) is an essential step in the diagnosis of the disease, showing in typical cases the association of nodules, cavitary nodules and cystic lesions with both thick and thin walls. The macrophage alveolitis observed in bronchoalveolar lavage (BAL) is not specific and reflects the smoking habits of the patients. BAL is useful to eliminate the presence of an infectious agent or other infiltrative lung disorders that can occur in young adults. In contrast to what was initially hoped, the sensitivity of the identification of increased numbers of LC in the BAL from patients with pulmonary LCH is weak in most cases. The definite diagnosis of pulmonary LCH requires the identification of LC granulomas, usually obtained by surgical lung biospy guided by lung HRCT. In pratice, however, lung biopsy is not systematically performed and is discussed on a case by case basis. A better understanding of the mecanisms involved in the pathogenesis of pulmonary LCH is essential and should help in the development of more specific therapeutic strategies for patients with this orphan disease for which no efficient treatment is currently available.