Pulmonary fibrosis is a chronic, progressive, irreversible fibroproliferative (nonneoplastic) disease of the lungs and the most common cause of interstitial pneumonia. The condition is characterized by the formation of scar tissue in the lungs. Pulmonary fibrosis is most commonly idiopathic, although in some instances, it occurs secondary to other disorders such as familial pulmonary fibrosis, Hermansky-Pudlak syndrome, and short telomere syndromes.

Typical signs and symptoms include exertional dyspnea, chronic dry cough, crackles, and fatigue. Digital clubbing occurs in about half of patients and, in the later stages of illness, right heart failure and cor pulmonale may be noted. Onset is typically in patients aged 50-70, with smokers at higher risk. It may be associated with pharmaceuticals such as cyclophosphamide, bleomycin, nitrosureas, methotrexate, and nitrofurantoin; radiation therapy; and environmental exposures to stone, metal, wood, and organic dusts. Men are affected more often than women.

Prognosis is poor for severely progressed cases due to impaired breathing, concomitant illness, and complications. Common complications include emphysema, pulmonary hypertension, cor pulmonale, and pneumonia. Patients with pulmonary fibrosis have a fivefold increase in risk of lung cancer compared with the general population. Life expectancy may be only 3-5 years following diagnosis. There is no known cure.