The gene variation, known as PTPN22, is found in approximately 16 percent (or one in six) of healthy Caucasians in the United States. However, nearly one in four (or 23 percent) lupus patients carry this variant, which has also now been associated with risk for type 1 diabetes and rheumatoid arthritis. The study is published in the September edition of the American Journal of Human Genetics.
"This appears to be a very important gene for lupus," said Timothy W. Behrens, M.D., professor of medicine, Medical School, and principal investigator, "and this is the first time we have identified a variant that predisposes to many different autoimmune diseases. We hope that this discovery will lead to the identification of other genes associated with lupus and other immune disorders." Behrens believes that dozens of genes may be responsible for lupus and that discovering the combination of these genes will be important to developing better diagnosis and treatment of the disease.

In SLE, a person's immune system begins attacking its own tissues. Organs commonly targeted in SLE include the skin, kidneys, joints, lungs, and the central nervous system. The severity of disease and the response to therapy vary widely between patients, said Behrens, and this leads to significant challenges in the diagnosis and management of lupus. "If we know which genes predispose a person to lupus, we may be able to diagnose and treat the disease earlier," he said. "In addition to discovering which combination of genes lead to lupus and other immune diseases, we also hope this information will help us identify new drugs and therapies."