Desquamative interstitial pneumonitis UMLS:C0238378 Filling of the alveoli with alveolar macrophages The name originated from the belief that the dominant histologic feature was desquamation of epithelial cells. However, this is now recognized to be intra-alveolar macrophage accumulation rather than desquamation of epithelial cells as originally thought by Liebow and Carrington. In adults the condition is almost invariable associated with cigarette smoke. However, rare cases occur in nonsmokers, some of whom have had exposure to environmental inhalation exposures including passive exposure to cigarette smoke. In children genetically caused surfactant dysfunction syndromes may have the histological pattern of DIP. Intra-alveolar accumulation of macrophages Filling of the alveoli with desquamated epithelial cells Diffuse filling of the distal airspaces of the lungs, the alveoli, with macrophages. Desquamative interstitial pneumonitis (DIP) is characterized additionally by thickened alveolar septa and by a sparse inflammatory infiltrate that often includes plasma cells and occasional eosinophils. The alveoli are lined by plump cuboidal pneumocytes. Lymphoid aggregates may be present. HP:0005942 SNOMEDCT_US:8549006 Abnormal pulmonary interstitial morphology