Pulmonary fibrosis (also known as interstitial lung disease or ILD) is a long-term disease where the lungs (pulmonary) become scarred (fibrosis). The scarring causes the part of the lung where oxygen is moved to the blood (interstitial) to become thick and stiff. If the reason or cause of the disease is unknown, it is called idiopathic. Pulmonary fibrosis is a restrictive disease because it is hard to fully expand the lungs when taking a breath in i.e., the lungs are restricted when taking a breath in.
