What is interstitial lung disease?
ILD is a large family of conditions that affect the tissue around the lungs' air sacs.
Why this matters
The main things to know
- ILD is not one disease — it is a family of more than 200 conditions.
- It affects the interstitium, the tissue that supports your lungs' tiny air sacs.
- Different types behave very differently, so your experience may not match someone else's.
Want a quick plain-language summary of this page?
Your lungs contain millions of tiny air sacs called alveoli, where oxygen passes into your blood. Around and between these air sacs is a delicate layer of tissue called the interstitium.
In interstitial lung disease (ILD), this tissue becomes inflamed, scarred (this is called fibrosis), or both. When the tissue thickens, it can be harder for oxygen to move from your lungs into your bloodstream. This is why many people with ILD notice breathlessness, especially with activity, and a dry cough.
ILD is a family, not a single illness
There are more than 200 types of ILD. Some are linked to an autoimmune condition, some to exposures (like dust, mold, or certain medications), and some have no clear cause. Idiopathic pulmonary fibrosis (IPF) is one specific type.
Because the types differ so much, the path each person takes is different. Some forms stay stable, some improve when a cause is found and removed, and some are progressive. Your care team can explain where your situation fits.
Your safe next step
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Reviewed by Dr. Youmna Abdelghany, MD
Pulmonary Disease & Critical Care Medicine
- Last reviewed:
- May 20, 2026
- Next review:
- May 20, 2027
- Reading level:
- Grade 6–8
Sources (3)
- Interstitial lung diseases — NHLBI (NIH) (opens a new site)
- Patient education series — American Thoracic Society (opens a new site)
- Pulmonary fibrosis resources — Pulmonary Fibrosis Foundation (opens a new site)