Interstitial lung disease (ILD) is an umbrella term for a large collection of connected lung problems that affect the interstitium, the tissue surrounding air sacs, blood vessels and airways in the lungs.

More than 200 lung disorders fall under interstitial lung disease, the most common of which cause progressive scarring of lung tissue. However, despite the wide variety of types, ILD is very rare, affecting between 2 to 20 per 100,000 people. Common symptoms of ILD include shortness of breath—at rest or during exertion—and a dry cough.

"This is a very diverse group of disorders that can range from inflammation to scarring [of the lungs]," said Stacey-Ann Brown, M.D., a pulmonologist and assistant professor of medicine at Johns Hopkins University in Baltimore, Maryland.

The most widely studied and common ILD is idiopathic pulmonary fibrosis (IPF), the word "idiopathic" meaning there is no known cause. IPF is more likely to progress than not, and for patients who have progressive