Non-infectious inflammation of the interstitial lung tissue of unknown etiology. this category includes desquamative interstitial pneumonia, usual interstitial pneumonia, lymphocytic interstitial pneumonia, acute interstitial pneumonia, and nonspecific interstitial pneumonia.

Idiopathic interstitial pneumonia (IIP), or noninfectious pneumonia are a class of diffuse lung diseases. These diseases typically affect the pulmonary interstitium, although some also have a component affecting the airways (for instance, cryptogenic organizing pneumonitis)...