Learn About Cryptogenic Organizing Pneumonia

Cryptogenic organizing pneumonia (COP) is a form of interstitial lung disease where the small airways (bronchioles) and alveoli (tiny air sacs) become inflamed, leading to difficulty breathing and flu-like illness.  

Key Facts

  • Although the word "pneumonia" is in the name, COP is not an infection. Instead, organizing pneumonia refers to organized swirls of inflammatory tissue filling the small bronchioles and alveoli.
  • COP is only diagnosed when all other possible causes of pneumonia have been eliminated and can cause severe lung damage if left untreated.
  • When treated with corticosteroids, most people recover quickly.

What Causes COP?

The condition is called “cryptogenic” because in most cases, the cause is unknown. Doctors believe that there are many possible causes including 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. COP has also been associated with lung abscesses, lung cancer and lymphoma.

Who Is at Risk?

Men and women are equally 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. A condition similar to COP may occur as a side effect of certain medications.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: March 6, 2020

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