Disorders in which the immune system malfunctions and reacts against the body’s own tissues
If a person is healthy, the cells of the immune system are able to distinguish between the body tissues and foreign organisms such as bacteria and viruses. If someone has an autoimmune disorder, the immune system mistakenly interprets the body’s own tissues as foreign. As a result, antibodies or white blood cells are formed that attack the body tissues and try to destroy them.
The underlying cause of this abnormal immune reaction is unclear, but it can run in families. Certain factors, such as some viral infections and reactions to particular drugs, may trigger an autoimmune reaction in susceptible people. Hormonal factors may also play a part, since these disorders occur more often in women than in men. Autoimmune disorders are less common in elderly people and in children.
In some autoimmune disorders, the tissues of a single organ are damaged, preventing normal function. Examples of organs that may be affected by these disorders include the thyroid gland in Hashimoto’s thyroiditis (see Thyroiditis), the pancreas in diabetes mellitus, the adrenal glands in Addison’s disease, and various joints in rheumatoid arthritis.
A second group of autoimmune disorders affects connective tissue, the material that holds together the structures of the body (see Scleroderma, and Systemic lupus erythematosus). In these disorders, the immune system may react against connective tissue anywhere in the body.
If your doctor suspects an autoimmune disorder, he or she may arrange for blood tests to assess immune function and look for evidence of inflammation. The treatment of autoimmune disorders depends on which organs are affected. In Hashimoto’s thyroiditis or Addison’s disease, damage to the affected organs leads to a deficiency in the hormones they normally produce. Replacement of deficient hormones often restores health. In other cases, the aim of treatment is to block the abnormal immune reactions with drugs such as immunosuppressants or corticosteroids or reduce symptoms with nonsteroidal anti-inflammatory drugs.
The outlook for people who have autoimmune disorders depends on the amount of damage to the body’s tissues and organs. Autoimmune disorders are usually lifelong, but the symptoms can often be controlled with drugs. In some cases, serious complications such as kidney failure may develop.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.