Learn About Cryptogenic Organizing Pneumonia (COP) | American Lung Association

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Learn About Cryptogenic Organizing Pneumonia (COP)

Cryptogenic organizing pneumonia (COP) is a lung condition affecting the small airways (bronchioles) and alveoli (tiny air sacs). The cause of COP is unknown.

It was previously known as idiopathic bronchiolitis obliterans with organizing pneumonia (BOOP).

Key Facts

  • "Cryptogenic" refers to a condition where the cause is unknown.
  • Cryptogenic organizing pneumonia (COP) is a form of organizing pneumonia (OP) for which no specific cause is known
  • Although the word "pneumonia" is in the name, COP is not an infection.
  • In most cases, gradual onset of shortness of breath and dry cough are the most common symptoms.
  • COP is usually treated with oral steroids.

What Is COP?

COP is a rare condition in which swirls of inflammation block the very small airways (bronchioles) and air sacs in the lung (alveloar sacs). When the cause of the inflammation is unknown, it is called "cryptogenic." COP used to be called "bronchiolitis obliterans organizing pneumonia, or "BOOP", but this term is no longer used.   

How COP Affects Your Body

Symptoms can begin gradually, over a few weeks to months. COP often begins with what seems like a flu-like illness. Most patients experience shortness of breath with exertion, dry cough and weight loss. If the disease progresses shortness of breath can be present even at rest.  In rare cases, patients may have chest pain, joint pain, night sweats or coughing up blood. 

How Serious Is COP?

COP is a condition that has the potential to cause severe lung damage and may require hospitalization.

Significant improvement usually occurs with proper treatment. Patients should be monitored as recurrences are common. Most people recover after weeks or months of treatment with a steroid such as prednisone.


    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


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