Sarcoidosis is an inflammatory disease without a known cause and without a cure. It occurs in individuals throughout the world. Sarcoidosis 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. There are many theories about the cause of sarcoidosis, including environmental exposure, a genetic (inherited) tendency to develop sarcoidosis, viral infection, immune system overactivity, or a combination of these factors. Treatment is based on an individual's symptoms and the degree to which involved organs are affected.