Idiopathic interstitial pneumonias

The idiopathic interstitial pneumonias (IIPs) comprise a group of diffuse lung diseases of unknown aetiology that primarily involve the pulmonary interstitium—the area between the alveolar epithelium and capillary endothelium, as well as the septal and bronchovascular tissues that make up the fibrous framework of the lung. These primarily interstitial processes, however, frequently also involve the airways, vasculature, and alveolar airspaces. The underlying pathological process is one of varying degrees of inflammation and fibrosis.