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What is sarcoidosis?

Sarcoidosis – also called sarcoid – is a condition where cells in your body clump together to make small lumps called granulomas.

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What is sarcoidosis?

Sarcoidosis – also called sarcoid – is a condition where inflamed cells clump together to make small lumps called granulomas. These granulomas can develop in any part of your body.

They are most commonly found in the lungs and the lymph glands which drain the lungs. They can also affect your skin, eyes, joints, heart, nervous system, liver, spleen, muscles, nose and sinuses.

When lots of granulomas develop in one area, they begin to affect how well that part of your body works. This causes symptoms. The inflammation, which is usually reversible, can sometimes progress to scarring, which isn’t reversible.

What are the effects of sarcoidosis?

Sarcoidosis affects people in lots of different ways. It can cause symptoms in just one part of your body or many parts at the same time. Though sarcoidosis isn’t always a lung condition, the lungs are affected in about 90% of cases. When the lungs are affected, it’s called pulmonary sarcoidosis.

Who gets sarcoidosis?

You can get sarcoidosis at any age, but it commonly affects adults in their 30s or 40s. It’s not a common condition: in the UK 4,500 people were diagnosed with the condition in 2012. It’s very rare for children to get sarcoidosis.

What causes sarcoidosis?

We don’t know what causes sarcoidosis. But we do know it’s related to your immune system behaving in a way it shouldn’t. This is probably a response to various triggers in the environment. 

Normally your immune system fights infections by releasing white blood cells into your blood to destroy germs. This causes the affected part of your body to become inflamed, making it swollen or red. Researchers think that sarcoidosis could be caused by something in the environment that stops your immune system working properly.

Research also suggests that, for some people, the risk of getting sarcoidosis is related to their genes. Sometimes, more than one family member can get sarcoidosis. But there’s no evidence that it’s infectious. 

Next: What are the symptoms of sarcoidosis? >

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Last medically reviewed: January 2020. Due for review: January 2023

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.