Pulmonary fibrosis is a condition in which there is diffuse fibrosis of lung parenchyma with a resultant impairment of gas transfer and ventilation-perfusion mismatching.

Fibrosis within the lung may be:

• replacement fibrosis, secondary to disorders such as:
• infarction
• pneumonia
• tuberculosis

• focal fibrosis, in response to irritants such as:
• silica
• coal dust

• interstitial fibrosis:
• cryptogenic (idiopathic) fibrosing alveolitis
• extrinsic allergic alveolitis