Doctors don't know the exact cause of sarcoidosis. Some people appear to have a genetic predisposition to developing the disease, which may be triggered by exposure to specific bacteria, viruses, dust or chemicals. Researchers are still trying to pinpoint the genes and trigger substances associated with sarcoidosis.

Normally, your immune system helps protect your body from foreign substances and invading microorganisms, such as bacteria and viruses. But in sarcoidosis, some immune cells collect in a pattern of inflammation called granulomas. As granulomas build up in an organ, the function of that organ can be affected.

Jan. 10, 2013