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What Causes Sarcoidosis?
The cause of sarcoidosis is autoimmune.

Scientists think that sarcoidosis develops when your immune system responds to something in the environment (e.g., bacteria, viruses, dust, chemicals) or perhaps to your own body tissue (autoimmunity).

Normally, your immune system defends your body against things that it sees as foreign and harmful. It does this by sending special cells to the organs that are being affected by these things. These cells release chemicals that produce inflammation around the foreign substance or substances to isolate and destroy them.

In sarcoidosis, this inflammation remains and leads to the development of granulomas or lumps.

Scientists have not yet identified the specific substance or substances that trigger the immune system response in the first place. They also think that sarcoidosis develops only if you have inherited a certain combination of genes.

The course of the disease varies greatly among people.

• In many people, sarcoidosis is mild. The inflammation that causes the granulomas may get better on its own. The granulomas may stop growing or shrink. Symptoms may go away within a few years.
• In some people, the inflammation remains but doesn't get worse. You may also have symptoms or flare-ups and need treatment every now and then.
• In other people, sarcoidosis slowly gets worse over the years and can cause permanent organ damage. Although treatment can help, sarcoidosis may leave scar tissue in the lungs, skin, eyes, or other organs. The scar tissue can affect how the organs work. Treatment usually does not affect scar tissue.

Changes in sarcoidosis usually occur slowly (e.g., over months). Sarcoidosis does not usually cause sudden illness. However, some symptoms may occur suddenly. They include:

• Disturbed heart rhythms
• Arthritis in the ankles
• Eye symptoms.

In some serious cases in which vital organs are affected, sarcoidosis can result in death.

Sarcoidosis was once thought to be an uncommon condition. It's now known to affect tens of thousands of people throughout the United States. Because many people who have sarcoidosis have no symptoms, it's hard to know how many people have the condition.

Sarcoidosis was identified in the late 1860s. Since then, scientists have developed better tests to diagnose it and made advances in treating it.