idiopathic pulmonary fibrosis
(IH-dee-oh-PA-thik PUL-muh-NAYR-ee fy-BROH-sis)
A disease in which the alveoli (tiny air sacs at the end of the bronchioles in the lungs) are overgrown with fibrous tissue. The cause of the disease is unknown and it gets worse over time. Symptoms include difficult, painful breathing and shortness of breath.