No gene or group of genes has been proven to cause lupus. Lupus does, however, appear in certain families, and certain genes have been identified as contributing to the development of lupus, but these associations alone are not enough to cause the disease. This is especially evident with twins who are raised in the same environment and have the same inherited features yet only one develops lupus. Although, when one of two identical twins has lupus, there is an increased chance that the other twin will also develop the disease (25 percent chance for identical twins; 2-3 percent chance for fraternal twins). Lupus can develop in people with no family history of lupus, but there are likely to be other autoimmune diseases in some family members.