What is interstitial lung disease (ILD)?

Interstitial lung disease (ILD), is a collective name for a group of lung diseases affecting the interstitium (the tissue and space around the air sacs or alveoli of the lungs).

ILD’s are a group of more than 100 diseases that lead to progressive lung damage. In some ILD’s the cause is unknown (idiopathic) others are related to auto-immune disorders, infections, genetics, or reactions to drugs or environmental irritants.

Prevalence rate is estimated to be 15-25 per 100,000 but this figure increases with age giving a current UK prevalence of approximately 15,000.1 Prevalence remains relatively low because unfortunately about 5000 patients with IPF (Idiopathic Pulmonary Fibrosis) per year die of their disease.

ILD’s are slightly more common in men than women and tend to affect people over 65 years of age.2

What do terms mean in ILD?

  • Interstitium: the tissue and space around the alveoli.
  • Fibrosis: thickening and scarring of connective tissue.
  • Pulmonary: relating to the lungs.


  1. British Thoracic Society Reports September 2014 ISSN 2040-2023 VOL. 6 ISSUE 3 2014
  2. CHSS booklet: Living with Idiopathic Pulmonary Fibrosis