Sjögren's ("SHOW-grins") syndrome is a chronic disease in which white blood cells attack the moisture-producing glands. The hallmark symptoms are dry eyes and dry mouth, but it is a systemic disease, affecting many organs and may cause fatigue. It is one of the most prevalent autoimmune disorders, striking as many as four million Americans. Sjögren's syndrome (SS) is defined as primary SS when it occurs by itself. When SS follows another connective tissue disease, such as lupus or rheumatoid arthritis, it is termed secondary SS.