Interstitial (in-tur-STISH-ul) lung disease, also called ILD, describes a large group of conditions. Most of these conditions cause inflammation and progressive scarring of lung tissue. As part of this process, lung tissue thickens and stiffens, making it hard for the lungs to expand and fill with air. At some point, the scarring from interstitial lung disease makes it harder to breathe and get enough oxygen into the bloodstream. Many people with ILD are short of breath with activity and may have a bothersome dry cough. Interstitial lung disease can have many causes, including long-term exposure to hazardous materials such as asbestos. Some types of autoimmune diseases, such as rheumatoid arthritis, also can cause interstitial lung disease. But the cause isn't known sometimes. ILD can have many causes, so treatment varies. The disease may get worse slowly or rapidly at a pace that often can't be predicted. Once lung scarring occurs, it generally isn't reversible. Treatment focuses on keeping more scarring from occurring, managing symptoms and making quality of life better. Medicines may slow the damage of interstitial lung disease, but many people never fully use their lungs again. Lung transplant is an option for some people who have ILD.