Sarcoidosis is a disease characterized by inflammatory lumps (granulomas) that form in multiple organs. It can be either short- or long-term and can affect any organ, most often the lungs and lymph nodes. The granulomas seem to form as an overreaction to an unknown threat to the body.

The cause of sarcoidosis is not known, but it appears that some patients have genetic factors that make them susceptible. It may also affect different races, ethnic groups and populations in varying ways. For example, Japanese people are more likely to be affected in the heart and eyes, whereas in Northern Europeans the skin is affected along with another organ, such as the lungs. The disease may be related to infections similar to tuberculosis. Environmental factors, such as exposure to potentially toxic substances, may increase the risk of developing it.

Sarcoidosis usually has minor symptoms or none at all. Symptoms depend greatly on which organs are affected and to what extent. General symptoms include fever, fatigue and an overall unwell feeling. Symptoms of sarcoidosis in the lungs include shortness of breath, cough and chest pain.

Sarcoidosis is often first detected by x-ray. A series of other tests, including a biopsy of affected tissue, confirm diagnosis. The criteria for diagnosis are detection of the characteristic symptoms and abnormalities, particularly on a chest x-ray, ruling out infections and finding sarcoidosis granulomas in biopsy.

Many cases of sarcoidosis do not need treatment, but the disease can be serious and sometimes even fatal when it affects vital organs. When treatment is required, corticosteroids are normally used. Relapse is much more common when the condition is serious enough that medical treatment is required. Tests (e.g., breathing tests) are performed for a few years to monitor the disease whether or not treatment is required.