Sarcoidosis is a disease characterized by the growth of tiny collections of inflammatory cells (granulomas) in any part of the body, most commonly the lungs and lymph nodes, but it can also affect the eyes, skin, heart, and other organs. The exact cause of sarcoidosis is unknown, but experts think it results from the bodys immune system responding to an unknown substance. Some research suggests that infectious agents, chemicals, dust, and a potential abnormal reaction to the bodys own proteins (self-proteins) could be responsible for the formation of granulomas in people who are genetically predisposed.

While the causes of sarcoidosis are not known, it is associated with increased immune system activity. This causes clusters of immune cells called granulomas to infiltrate organs and lymph nodes. Health experts think that having certain genes makes it more likely for a person to develop sarcoidosis. Things that may trigger the disease include infections with bacteria or viruses. Contact with dust or chemicals may also be triggers. The disease is more common in African Americans and White people of Scandinavian heritage. More women than men have the disease. The disease often begins between ages 20 and 40. Sarcoidosis is rare in young children. A person with a close blood relative who has sarcoidosis is nearly 5 times as likely to develop the condition.

In summary, the exact cause of sarcoidosis is unknown, but it is associated with increased immune system activity and the formation of granulomas in people who are genetically predisposed. Infections with bacteria or viruses, as well as contact with dust or chemicals, may also trigger the disease.