Understanding Sarcoidosis -- The Basics

What Is Sarcoidosis?

Sarcoidosis is a chronic disease that can affect multiple organs -- eyes, joints, skin -- but lungs are involved in 95% of cases. The disease is characterized by the buildup of immune system cells in organs that form small clusters called granulomas, a type of inflammation of the involved tissues.

While the disease can affect anybody, African-Americans have a lifetime risk of 2.4% for developing sarcoidosis, while whites have a risk of 0.85%. It occurs most commonly between the ages of 20 and 40, although it can occur in children, and there is a second peak, particularly in women, after age 50.

Because the symptoms of sarcoidosis can be vague and may be mistaken for other diseases, it's difficult to estimate how common it is. In the U.S., an estimated 10 to 40 in 100,000 people have sarcoidosis.

Sarcoidosis is not cancer; nor is it contagious. Although it can occur in families, it is not inherited. Usually the disease is not disabling; most people with sarcoidosis live normal lives. In fact, in the majority of cases, the disease appears only briefly and disappears on its own. About 20% to 30% of people with sarcoidosis are left with some permanent lung damage, and in 10% to 15% of patients the disease is chronic. Although it is rare, death from sarcoidosis can occur if the disease causes serious damage to vital organs, such as the brain, lungs, or heart.

What Causes Sarcoidosis?

Researchers believe sarcoidosis is associated with an abnormal immune system response, but what triggers this response is not known. Nor do doctors know whether heredity, environment, or lifestyle affects the development, severity, or length of the disease. These are questions that researchers are trying to answer.

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