Sarcoidosis is an inflammatory disease that usually affects the lungs, causing granulomas (inflammatory nodules). However, it can affect other organs, including the heart, liver, lymph nodes, skin, and eyes. Its symptoms vary depending on the areas of the body affected. Sometimes sarcoidosis is found incidentally, such as when a chest x-ray is taken for another reason. Although the cause is not known, it is thought that there is a genetic (inherited) tendency to develop an immune reaction when exposed to certain particles, which may result in organ damage. Sarcoidosis is not contagious, but proteins from certain bacteria may be involved in triggering the reaction. The January 26, 2011, issue of JAMA includes an article about sarcoidosis. This Patient Page is based on one previously published in the November 1, 2006, issue of JAMA.