Pulmonary fibrosis is a chronic and progressive lung disease characterized by the formation and accumulation of fibrotic (i.e., scar) tissue in the lungs. This leads to thickening of the walls of the alveoli (small air sacs in the lungs) and interstitial scarring, which restricts lung expansion and impairs their function.

Symptoms of pulmonary fibrosis may include shortness of breath, chronic cough, fatigue, weakness, chest pain, and weight loss. These symptoms may gradually worsen over time.

Causes of pulmonary fibrosis can be diverse, including exposure to toxic substances (such as asbestos, dust), infections, autoimmune diseases, and genetic factors. However, for many people, the cause of pulmonary fibrosis remains unknown, and such cases are termed idiopathic pulmonary fibrosis (IPF).