No one knows the exact cause or causes of autoimmune diseases (also called autoimmune disorders). However, doctors do know that you cannot catch these diseases from another person.
Most research scientists believe that there is a link between autoimmune diseases, a person's genes, and factors in the environment. Researchers believe that if you have a certain gene or combination of genes, you may be at higher risk for autoimmune disease but that you won't get the disease until something triggers your immune system. Triggers may include the sun, infections, drugs, or pregnancy.