Cryptogenic organizing pneumonia (COP) is the idiopathic form of organizing pneumonia (OP) and is considered a rare type of interstitial lung disease. OP, including COP, is a lung disease where organized swirls of inflammatory tissue the small airways (bronchioles) and alveoli (tiny air sacs) become inflamed causing flu-like symptoms.
Key Facts
- Although the word "pneumonia" is in the name, COP is not an infection and is not contagious.
- The condition is called “idiopathic” and “cryptogenic” when the cause is unknown.
- When treated with corticosteroids, most people recover quickly.
What Causes COP?
While the condition is called “cryptogenic” when the cause is unknown, if the underlying cause can be determined, it is called secondary organizing pneumonia. This is important because the management of secondary OP depends on the known cause and it is managed differently from COP.
There are many possible causes for OP including autoimmune diseases, radiation therapy, exposure to certain chemicals, exposure to birds, post respiratory infections, as a side-effect of organ transplantation or as a side effect from taking certain medications. OP has also been associated with lung abscesses, lung cancer and lymphoma.
Who Is at Risk?
Men and women are both affected and the average age of someone diagnosed with COP is between 50 to 60 years old. Inflammatory diseases such as lupus, rheumatoid arthritis and scleroderma can increase someone’s risk of developing COP.
Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.
Page last updated: October 22, 2025
