Once thought to be an uncommon condition, sarcoidosis is an immune system disease that is now known to affect tens of thousands of people throughout the United States. It is characterized by tiny lumps of cells in various organs in the body. These lumps are called granulomas because they look like grains of sugar or sand, and they are so small they can be seen only with a microscope. These lumps can grow and clump together; if many granulomas form in an organ, they may affect how the organ works.
Sarcoidosis usually starts in the lungs or lymph nodes, but may also affect the skin, liver, and eyes. Most people with the disease have no symptoms, and there is no known way to prevent it. It should be noted that sarcoidosis is not a form of cancer.
(For a closer look at this disease and its progression, click Sarcoidosis.)