**5. Interstitial lung disease**

Interstitial lung disease (ILD) describes a collection of more than 200 lung disorders that involve inflammation and fibrosis of the alveoli, distal airways, and septal interstitium of the lungs. Typically, ILD presents with progressive breathlessness, lung crackles, and a diffusely abnormal chest radiograph. This disorder can be caused by long-term exposure to hazardous materials or by some types of autoimmune diseases, such as rheumatoid arthritis. In some cases, however, the etiology remains unknown. The following sections summarize the latest proteomic studies aimed at clarifying the pathophysiological mechanisms involved in the development and progression of ILD. All recent proteomic studies in this area based on electrokinetic approaches have been performed on BALf.
