Normally the immune system's white blood cells help protect the body from harmful substances, called antigens. Examples of antigens include bacteria, viruses, toxins, cancer cells, and blood or tissues from another person or species. The immune system produces antibodies that destroy these harmful substances.
In patients with an autoimmune disorder, the immune system can't tell the difference between healthy body tissue and antigens. The result is an immune response that destroys normal body tissues. This response is a hypersensitivity reaction similar to the response in allergic conditions.
In allergies, the immune system reacts to an outside substance that it normally would ignore. With autoimmune disorders, the immune system reacts to normal body tissues that it would normally ignore.
What causes the immune system to no longer tell the difference between healthy body tissues and antigens is unknown. One theory is that some microorganisms (such as bacteria or viruses) or drugs may trigger some of these changes, especially in people who have genes that make them more likely to get autoimmune disorders.
An autoimmune disorder may result in:
The destruction of one or more types of body tissue
Abnormal growth of an organ
Changes in organ function
An autoimmune disorder may affect one or more organ or tissue types. Organs and tissues commonly affected by autoimmune disorders include:
Which treatments are used depends on the specific disease and your symptoms.
Some patients may need supplements to replace a hormone or vitamin that the body is lacking. Examples include thyroid supplements, vitamins such as B12, or insulin injections.
If the autoimmune disorder affects the blood, you may need blood transfusions.
People with autoimmune disorders that affect the bones, joints, or muscles may need help with movement or other functions.
Medicines are often prescribed to control or reduce the immune system's response. They are often called immunosuppressive medicines. Such medicines may include corticosteroids (such as prednisone) and nonsteroid drugs such as azathioprine, cyclophosphamide, mycophenolate, sirolimus, or tacrolimus.
The outcome depends on the disease. Most autoimmune diseases are chronic, but many can be controlled with treatment.
Symptoms of autoimmune disorders can come and go. When symptoms get worse, it is called a flare-up.
Complications depend on the disease. Side effects of medications used to suppress the immune system can be severe, such as infections that can be hard to control.
Calling your health care provider
Call your health care provider if you develop symptoms of an autoimmune disorder.
There is no known prevention for most autoimmune disorders.
Goronzy JJ, Weyand CM. The innate and adaptive immune systems. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007: chap 42.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.