Sjögren's syndrome is a common rheumatoid autoimmune disease—about 1% of the population suffers from it at any given time. It is caused when antibodies attack the cells responsible for the production of saliva and tears. Many times, the symptoms—dry mouth and dry eyes—are the only effect of the disease and are often very mild. However, in severe cases, secondary complications can set in such as opportunistic infections and ulcerations caused by the lack of lubrication of the eye. These can often be life threatening. The autoimmune disorder can also spread to other organs, such as the lungs.