[Pattern of biological changes in interstitial lung diseases].

Interstitial lung diseases (ILD) are a part of a vast and heterogeneous clinicopathological entity. The work-up have to rule out a granulomatosis or a secondary cause, before making the diagnosis of an idiopathic ILD. The etiological diagnosis is based on a multidisciplinary approach integrating a network of clinical and paraclinical datas. If the diagnosis remains unclear, a lung biopsy is suggested with a transbronchial approach (mainly cryobiopsy) or with a surgical approach (video-assisted thoracoscopy). This review article mainly describes the biological analyses that contribute to explore ILDs.