Idiopathic interstitial pneumonitis (Q42932)

The idiopathic interstitial pneumonias (pneumonitises) are a subset of diffuse interstitial lung diseases of unknown etiology characterised by expansion of the interstitial compartment (i.e. that portion of the lung parenchyma sandwiched between the epithelial and endothelial basement membranes) with an infiltrate of inflammatory cells. The inflammatory infiltrate is sometimes accompanied by fibrosis, either in the form of abnormal collagen deposition or proliferation of fibroblasts capable of collagen synthesis.