Sarcoidosis is a disease of unknown cause that leads to inflammation. It can affect various organs in the body.
Normally, your immune system defends your body against foreign or harmful substances. For example, it sends 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 destroyed, the cells and the inflammation go away.

In people who have sarcoidosis, the inflammation doesn’t go away. Instead, some of the immune system cells cluster to form lumps called granulomas in various organs in your body.

Sarcoidosis can affect any organ in your body. However, it’s more likely to occur in some organs than in others. The disease usually starts in the lungs, skin, and/or lymph nodes (especially the lymph nodes in your chest).

The disease also often affects the eyes and the liver. Although less common, sarcoidosis can affect the heart and brain, leading to serious complications.

If many granulomas form in an organ, they can affect how the organ works. This can cause signs and symptoms. Signs and symptoms vary depending on which organs are affected. Many people who have sarcoidosis have no symptoms or mild symptoms.

Lofgren’s syndrome is a classic set of signs and symptoms that is typical in some people who have sarcoidosis. Lofgren’s syndrome may cause fever, enlarged lymph nodes, arthritis (usually in the ankles), and/or erythema nodosum (er-i-THE-ma no-DO-sum).

Erythema nodosum is a rash of red or reddish-purple bumps on your ankles and shins. The rash may be warm and tender to the touch.

Treatment for sarcoidosis also varies depending on which organs are affected. Your doctor may prescribe topical treatments and/or medicines to treat the disease. Not everyone who has sarcoidosis needs treatment.

The outcome of sarcoidosis varies. Many people recover from the disease with few or no long-term problems.

More than half of the people who have sarcoidosis have remission within 3 years of diagnosis. “Remission” means the disease isn’t active, but it can return.

Two-thirds of people who have the disease have remission within 10 years of diagnosis. People who have Lofgren’s syndrome usually have remission. Relapse (return of the disease) 1 or more years after remission occurs in less than 5 percent of patients.

Sarcoidosis leads to organ damage in about one-third of the people diagnosed with the disease. Damage may occur over many years and involve more than one organ. Rarely, sarcoidosis can be fatal. Death usually is the result of complications with the lungs, heart, or brain.

Poor outcomes are more likely in people who have advanced disease and show little improvement from treatment.

Certain people are at higher risk for poor outcomes from chronic (long-term) sarcoidosis. This includes people who have lung scarring, heart or brain complications, or lupus pernio (LU-pus PAR-ne-o). Lupus pernio is a serious skin condition that sarcoidosis may cause.

Research is ongoing for new and better treatments for sarcoidosis.