Sarcoidosis is an inflammatory disease that affects multiple organs in the body, but mostly the lungs and lymph glands. People with sarcoidosis form abnormal masses or nodules consisting of inflamed tissues in certain organs of the body.
As sarcoidosis progresses, microscopic lumps of a specific form of inflammation, called granulomas, appear in the affected tissues. In the majority of cases, these granulomas clear up, either with or without treatment. In the few cases where the granulomas do not heal and disappear, the tissues tend to remain inflamed and become scarred (fibrotic).
The symptoms of sarcoidosis can vary greatly, depending on which organs are involved. Most patients initially complain of a persistent dry cough, fatigue, and shortness of breath. Other symptoms may include reddish bumps or patches on the skin, swollen and painful joints, enlarged and tender lymph glands, and nervous system disorders.
In some people, symptoms may begin suddenly and subside in a short period of time. Others may have no outward symptoms at all even though organs are affected. Still others may have symptoms that appear slowly and subtly, but which last or recur over a long time span.
The exact cause of sarcoidosis is not known. It is a type of autoimmune disease associated with an abnormal immune response, but what triggers this response is uncertain. How sarcoidosis spreads from one part of the body to another is still being studied.