One of the functions of the immune system is to protect the body by reacting to invading microorganisms, such as viruses or bacteria, by producing antibodies or sensitized lymphocytes (types of white blood cells). Under normal conditions, an immune response cannot be triggered against the cells of your own body. In certain cases immune cells make a mistake and attack the very cells they are meant to protect. This can lead to a variety of autoimmune diseases.

The probability of developing an autoimmune disease is determined by a dominant genetic trait that is very common. In fact, it's estimated that 20 percent of the population has a genetic susceptibility. Women are more likely than men to be affected, and some estimates say that 75 percent of those affected are women. Most often, there are different autoimmune diseases within the same family, rather than the whole family having the same disease.

This genetic trait alone does not cause the development of autoimmune diseases. Scientists believe that other factors must be present in order for the disease process to begin.

If other members of your family have an autoimmune disease, remember to mention this while talking to your doctor about a diagnosis.

Updated March 2007