Fibrosis
The formation of excess fibrous scar tissue, replacing normal functioning tissue.
What it means
Fibrosis is the replacement of normal tissue by fibrous scar tissue, the end result of repeated or sustained injury and inflammation.
Scar tissue restores structural continuity but does not restore function. Fibrotic lung does not exchange gas; fibrotic liver does not perform liver work; fibrotic heart muscle does not contract.
Established fibrosis is generally permanent, which is why treatment of the underlying process aims to prevent it rather than reverse it.
In practice
Cirrhosis is advanced liver fibrosis. Pulmonary fibrosis describes scarring of lung tissue. Fibrosis also follows radiotherapy and surgery.
Note that cystic fibrosis is an unrelated inherited condition despite the name.
Why it matters
The practical implication is that early treatment matters. Liver fibrosis from fatty liver or alcohol can stabilise and partly regress if the cause is removed early; cirrhosis cannot.
Progressive breathlessness with a dry cough, particularly with fine crackles on examination, warrants investigation for pulmonary fibrosis.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026