Interstital Lung Disease (ILD) is a general term that includes a several chronic lung disorders that includes a several chronic lung disorders, including idiopathic pulmonary fibrosis. Interstital Lung Disease affects a part of the lung called the interstitum, which iis located between the lung's ari sacs (alvoli). In people with ILD, the interstitum is affected by fibrosis (Scarring).

Interstital lung disease develops in three stages:

• First, lung tissues is damaged somehow.
• Second, the walls of the air sacs (alvoli) become red & swollen
• Third, the interstital tissue starts to scar (this is called fibrosis), and the lungs become stiff.