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Causes
By Mayo Clinic staffDoctors don't know the exact cause of sarcoidosis, although they think it may occur when your immune system overreacts to an unknown toxin, drug or pathogen that enters your body through your airways, when you breathe.
It's also possible that some people have a genetic predisposition to developing sarcoidosis, which, when combined with an environmental trigger, produces the disease. Studies are ongoing to investigate the genetic and environmental components of this disease.
Normally, your immune system helps protect your body from foreign substances and invading microorganisms, such as bacteria and viruses. But in sarcoidosis, T-helper lymphocytes — white blood cells that play a key role in your immune response — seem to respond too strongly to a perceived threat. This triggers small, distinct areas of inflammation called granulomas.
As the disease progresses, granulomas can damage healthy tissue and cause scarring (fibrosis). For example, fibrosis may occur in the tissue between the air sacs in your lungs, stiffening your lungs and reducing the amount of air your lungs can hold.
