The cause of sarcoidosis isn't known. More than one factor may play a role in causing the disease.

Many researchers think that sarcoidosis develops when your immune system responds to a trigger, such as bacteria, viruses, dust, or chemicals by sending special cells to protect organs that are in danger. These cells release chemicals that recruit other cells to isolate and destroy the harmful substance. Inflammation occurs during this process. Once the harmful substance is gone, the cells and the inflammation go away. In people who have sarcoidosis, the inflammation doesn't go away and some of the immune system cells cluster to form lumps called granulomas in various organs in your body.

Genetics also may play a role in sarcoidosis. Researchers believe that sarcoidosis occurs if you have certain genes that raise your risk for the disease and you are exposed to something that triggers your immune system.

Researchers continue to try to pinpoint the genes that are linked to sarcoidosis.