Cryptogenic organising pneumonia (COP)

Cryptogenic organising pneumonia (COP) is a rare lung condition and a type of interstitial lung disease. It’s sometimes called bronchiolitis obliterans organising pneumonia (BOOP).

COP causes inflammation and scarring in the small airways and air sacs in your lungs.

On this page, we cover what causes COP, what the symptoms of cryptogenic organising pneumonia are and how COP is treated.

What causes cryptogenic organising pneumonia?

The condition is called cryptogenic because the cause is unknown. It can also be called idiopathic. Although COP has pneumonia in its name, it is not an infection. The fact that many cases respond to immunosuppressant drugs suggests that there is an autoimmune component to COP.

Our bodies have an immune response to fight infection. Sometimes the immune response can be too strong – it doesn’t only fight the infection but also causes other damage to the body. In these cases, immunosuppressant drugs are used to reduce the body’s immune response. This is called immune suppression.


What are the symptoms of COP?

COP symptoms closely mimic the symptoms of pneumonia. The most common symptoms of cryptogenic organising pneumonia are:

  • persistent dry cough
  • a high temperature – you might also sweat and shiver
  • feeling generally unwell
  • feeling short of breath
  • loss of appetite and losing weight

“I had severe night sweats that lasted for months. I went to bed every night with a hairdryer and towels and change of bedding prepared for the 4am sweat! I’d never had these before, and in fact it’s now a warning sign to me if I get one, to get checked over again.” Fiona

As the condition is rare, it may take some time to get a diagnosis. Your health care professional will want to rule out other causes, including pneumonia or other conditions with pneumonia-like symptoms.


How is COP treated?

You will usually be given oral steroids, such as prednisolone, which are immunosuppressant drugs. In severe cases, you may be treated intravenously with infusions of a stronger steroid.

You’ll normally feel better in a few days. In most cases, you will notice a marked improvement within a week.

It can take several weeks or months to make a full recovery. The length of treatment varies considerably, but most people with COP will be treated for 6 to 12 months.

Some people get symptoms again when the steroid dose is reduced. They may need to take further immunosuppressant drugs.


Useful resources:

American Lung Association

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Download our COP information (PDF, 121KB)

Last medically reviewed: November 2019. Due for review: November 2022

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.