Autoimmune diseases are the result of the immune system reacting against the body’s own cells. Normally the immune system defends the body against antigens, such as foreign bodies, bacteria or viruses. Sometimes there is a malfunction and the immune system mistakes the body’s own tissues or organs for antigens and attacks them. Nearly any part of the body is susceptible to such an attack.

More than 80 medical conditions may be considered autoimmune diseases. Examples include type 1 diabetes, rheumatoid arthritis, lupus and multiple sclerosis. Autoimmune diseases affect between 14 and 24 million Americans, or up to 8 percent of the population, according to U.S. health agencies. Autoimmune diseases can affect anyone, but many of these conditions are more common in women.

The causes of autoimmune diseases are not completely understood. An inherited link, related to multiple genes, is recognized and is believed to make some people more susceptible to the diseases. However, people with identical genes (such as identical twins) only have a 15 to 50 percent chance of developing the same autoimmune disease (an average of a 30 percent chance). These occurrence rates indicate that some other trigger, such as exposure to an antigen or environmental factors, may activate the disease. Nutrition and hormones are also possibly involved.

With more than 80 possible autoimmune diseases, there are a variety of possible symptoms. Early symptoms are often nonspecific, such as fatigue, dizziness, and joint and muscle pain. In some cases, symptoms occur sporadically, which makes diagnosis difficult. Furthermore, autoimmune diseases may progress unnoticed for years until severe symptoms appear and prompt people to seek medical attention.

There is no known cure for autoimmune diseases. Initial treatment is aimed at repairing or replacing functions lost to tissue damage. In addition, treatment may involve immunosuppressive medications that reduce damage. Whatever treatment is used, it is likely to continue throughout the remainder of the patient’s life, and many side effects of these treatments are possible.

Autoimmune diseases are being studied in many current medical research projects. Topics of study include potential causes, improved diagnostic techniques and new treatment methods. With more advances anticipated in the future, physicians hope to reduce the occurrence and help provide cures for autoimmune diseases.