[Granulomatous interstitial lung diseases].

Sarcoidosis is sometimes severe and, in this setting, some investigations like thoracic computed tomography and pulmonaruy function tests constitute an angular stone. In 25% of cases, the presentation is not typical and diagnosis may be difficult. Some lung granulomatosis may share a very similar presentation with sarcoidosis according to clinic, imaging, serum biology, broncho-alveolar lavage and pathology (berylliosis, immuno-deficiency and drug- induced lung granulomatosis). Eventually, lung Langerhans histiocytosis is a very rare disease observed in young adults with heavy smoking habits and thoracic CT is the crucial investigation to reach diagnosis in 80% of cases.