An autoimmune disorder is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue. There are more than 80 different types of autoimmune disorders.

See also: Immune response

Normally the immune system's army of white blood cells helps 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.

But 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 allergies.

In allergies, the immune system reacts to an external substance that it normally would ignore. With autoimmune disorders, the immune system reacts to normal body tissues.

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) and 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:

• Red blood cells
• Blood vessels
• Connective tissues
• Endocrine glands such as the thyroid or pancreas
• Muscles
• Joints
• Skin

A person may have more than one autoimmune disorder at the same time. Examples of autoimmune (or autoimmune-related) disorders include:

• Hashimoto's thyroiditis
• Pernicious anemia
• Addison's disease
• Type I diabetes
• Rheumatoid arthritis
• Systemic lupus erythematosus
• Dermatomyositis
• Sjogren syndrome
• Lupus erythematosus
• Multiple sclerosis
• Myasthenia gravis
• Reactive arthritis
• Grave's disease
• Celiac disease - sprue (gluten sensitive enteropathy)

Symptoms of an autoimmune disease vary widely and depend on the specific disease.

A group of symptoms that occur with autoimmune diseases may include:

• Dizziness
• Fatigue
• General ill-feeling
• Low-grade fever

The health care provider will perform a physical exam. Specific signs vary widely and depend on the specific disease.

Tests that may be done to diagnose an autoimmune disorder may include:

• Erythrocyte sedimentation rate (ESR)
• C-reactive protein (CRP)

The goals of treatment are to reduce symptoms, control the autoimmune process, and maintain the body's ability to fight disease. 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, 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 cyclophosphamide, azathioprine, or tacrolimus.

The outcome depends on the specific disease. Most are chronic, but many can be controlled with treatment. Symptoms of autoimmune disorders can come and go. The sudden, severe development of symptoms is called a flare-up.

Complications depend on the specific disease. Side effects of medications used to suppress the immune system can be severe.

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.