Interstitial Lung Disease

Definition: Interstitial lung disease (ILD) refers to a broad range of conditions that have common clinical, physiological, and radiological features. ILD is not one disease, but several diseases that do not necessarily share a common histopathological or pathophysiological basis. By strict definition, ILD involves abnormalities of the interstitium, the potential space between the epithelial and capillary endothelium basement membranes within the alveolus. However, many of the conditions that have been traditionally included under the heading of ILD actually involve other anatomic structures within the lung. For this reason, the more general term “diffuse parenchymal lung disease” (DLPD) is now considered to be preferable, unless the nature of the disease is defined anatomically. However, the term ILD remains in common clinical usage.