What triggers autoimmune disorders is not known.
Symptoms vary depending on which disorder develops and which part of the body is affected.
Several blood tests are often used to check for an autoimmune disorder.
Treatment depends on the type of autoimmune disorder and often involves drugs that suppress the activity of the immune system.
(See also Overview of Allergic Reactions Overview of Allergic Reactions Allergic reactions (hypersensitivity reactions) are inappropriate responses of the immune system to a normally harmless substance. Usually, allergies make people sneeze; the eyes water and itch... read more .)
The immune system must first recognize Recognition The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more foreign or dangerous substances before it can defend the body against them. Such substances include bacteria, viruses, parasites (such as worms), certain cancer cells, and even transplanted organs and tissues. These substances have molecules that the immune system can identify and that can stimulate a response by the immune system. These molecules are called antigens. Antigens may be contained within cells or on the surface of cells (such as bacteria or cancer cells) or be part of a virus. Some antigens, such as pollen or food molecules, exist on their own.
Cells in a person's own tissues also have antigens. But normally, the immune system reacts only to antigens from foreign or dangerous substances, not to antigens from a person's own tissues. However, the immune system sometimes malfunctions, interpreting the body's own tissues as foreign and producing antibodies (called autoantibodies) or immune cells that target and attack particular cells or tissues of the body. This response is called an autoimmune reaction. It results in inflammation and tissue damage. Such effects may constitute an autoimmune disorder, but many people produce such small amounts of autoantibodies that an autoimmune disorder does not occur. Having autoantibodies Pain that seems to be coming from joints can sometimes be coming from structures outside the joints, such as ligaments, tendons, or muscles (see Introduction to the Biology of the Musculoskeletal... read more in the blood does not mean that a person has an autoimmune disorder.
There are many autoimmune disorders. Some of the more common autoimmune disorders include Graves disease Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more , rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more , Hashimoto thyroiditis Hashimoto Thyroiditis Hashimoto thyroiditis is chronic, autoimmune inflammation of the thyroid. Hashimoto thyroiditis results when the body attacks the cells of the thyroid gland—an autoimmune reaction. At first... read more , type 1 diabetes mellitus Type 1 diabetes Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more , systemic lupus erythematosus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic autoimmune inflammatory connective tissue disorder that can involve joints, kidneys, skin, mucous membranes, and blood vessel walls. Problems in the... read more (lupus), and vasculitis Overview of Vasculitis Vasculitic disorders are caused by inflammation of the blood vessels (vasculitis). Vasculitis can be triggered by certain infections or drugs or can occur for unknown reasons. People may have... read more . Additional disorders that are believed to be autoimmune include Addison disease Addison Disease In Addison disease, the adrenal glands are underactive, resulting in a deficiency of adrenal hormones. Addison disease may be caused by an autoimmune reaction, cancer, an infection, or some... read more , polymyositis Autoimmune Myositis Autoimmune myositis causes inflammation and weakness in the muscles (polymyositis) or in the skin and muscles (dermatomyositis). Muscle damage may cause muscle pain and muscle weakness may cause... read more , Sjögren syndrome Sjögren Syndrome Sjögren syndrome is a common autoimmune rheumatic disorder and is characterized by excessive dryness of the eyes, mouth, and other mucous membranes. White blood cells can infiltrate and damage... read more , progressive systemic sclerosis Systemic Sclerosis Systemic sclerosis is a rare, chronic autoimmune rheumatic disorder characterized by degenerative changes and scarring in the skin, joints, and internal organs and by blood vessel abnormalities... read more , many cases of glomerulonephritis Glomerulonephritis Glomerulonephritis is a disorder of glomeruli (clusters of microscopic blood vessels in the kidneys with small pores through which blood is filtered). It is characterized by body tissue swelling... read more (inflammation of the kidneys), and some cases of infertility.
Autoimmune reactions can be triggered in several ways:
A normal body substance is altered, for example, by a virus, a drug, sunlight, or radiation. The altered substance may appear foreign to the immune system. For example, a virus can infect and thus alter cells in the body. The virus-infected cells stimulate the immune system to attack.
A foreign substance that resembles a natural body substance may enter the body. The immune system may inadvertently target the similar body substance as well as the foreign substance. For example, the bacteria that cause strep throat have an antigen that is similar to an antigen in human heart cells. Rarely, the immune system attacks a person's heart after strep throat (this reaction is part of rheumatic fever).
The cells that control antibody production—for example, B cells (a type of white blood cell)—may malfunction and produce abnormal antibodies that attack some of the body's cells.
A substance in the body that is normally confined to a specific area (and thus is hidden from the immune system) is released into the bloodstream. For example, a blow to the eye can cause the fluid in the eyeball to be released into the bloodstream. The fluid stimulates the immune system to identify the eye as foreign and attack it.
Why something triggers an autoimmune reaction or disorder in one person (and not another) is usually unknown. However, heredity is sometimes involved. Some people have genes that make them slightly more likely to develop an autoimmune disorder. This slightly increased susceptibility to an autoimmune disorder, rather than the disorder itself, is inherited. In susceptible people, a trigger, such as a viral infection or tissue damage, may cause the disorder to develop.
Many autoimmune disorders are more common among women.
Symptoms vary depending on the disorder and the part of the body affected. Some autoimmune disorders affect certain types of tissue throughout the body—for example, blood vessels, cartilage, or skin. Other autoimmune disorders affect a particular organ. Virtually any organ, including the kidneys, lungs, heart, and brain, can be affected. The resulting inflammation and tissue damage can cause pain, deformed joints, weakness, jaundice, itching, difficulty breathing, accumulation of fluid (edema), delirium, and even death.
Blood tests that indicate the presence of inflammation may suggest an autoimmune disorder. Such tests include the following:
The erythrocyte sedimentation rate (ESR): This test measures how quickly red blood cells (erythrocytes) settle to the bottom of a test tube containing blood. When inflammation is present, the ESR is often increased because proteins that are produced in response to inflammation interfere with the ability of red blood cells to remain suspended in blood.
Complete blood count (CBC): This test includes determining the number of red blood cells in blood. This number is frequently decreased (anemia) because fewer red blood cells are produced when inflammation is present.
Because inflammation has many causes (many of which are not autoimmune), doctors often also do blood tests to detect different antibodies that can occur in people who have particular autoimmune disorders. Examples of these antibodies are
But even these antibodies sometimes occur in people who do not have an autoimmune disorder, so doctors usually use a combination of test results and the person's symptoms to decide whether an autoimmune disorder is present.
Drugs that suppress the immune system Drugs Used to Prevent Transplant Rejection Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more (immunosuppressants), such as azathioprine, chlorambucil, cyclophosphamide, cyclosporine, mycophenolate, and methotrexate, are often given, usually by mouth and often for a long time. However, these drugs suppress not only the autoimmune reaction but also the body's ability to defend itself against foreign substances, including microorganisms that cause infection and cancer cells. Consequently, the risk of certain infections and cancers increases.
Often, corticosteroids Corticosteroids: Uses and Side Effects Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more , such as prednisone, are given, usually by mouth. These drugs relieve inflammation as well as suppress the immune system. Corticosteroids given for a long time have many side effects. When possible, corticosteroids are used for a short time—when the disorder begins or when symptoms worsen. However, corticosteroids must sometimes be used indefinitely.
Certain autoimmune disorders (such as multiple sclerosis and thyroid disorders) are also treated with drugs other than immunosuppressants and corticosteroids. Treatment to relieve symptoms may also be needed.
Etanercept, infliximab, and adalimumab Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more block the action of tumor necrosis factor (TNF), a substance that can cause inflammation in the body. These drugs are very effective in treating rheumatoid arthritis and some other autoimmune disorders, but they may be harmful if used to treat certain other autoimmune disorders, such as multiple sclerosis. These drugs can also increase the risk of infection and certain skin cancers.
Certain drugs specifically target white blood cells. White blood cells help defend the body against infection but also participate in autoimmune reactions. These drugs include the following:
Abatacept Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more blocks the activation of one kind of white blood cell (T cell) and is used in rheumatoid arthritis.
Rituximab Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more , first used against certain white blood cell cancers, works by depleting certain white blood cells (B cells) from the body. It is effective in some autoimmune disorders, such as rheumatoid arthritis and certain disorders that cause inflammation of blood vessels (vasculitis Overview of Vasculitis Vasculitic disorders are caused by inflammation of the blood vessels (vasculitis). Vasculitis can be triggered by certain infections or drugs or can occur for unknown reasons. People may have... read more ), including granulomatosis with polyangiitis Granulomatosis with Polyangiitis Granulomatosis with polyangiitis often begins with inflammation of small- and medium-sized blood vessels and tissues in the nose, sinuses, throat, lungs, or kidneys. The cause is unknown. The... read more (formerly called Wegener granulomatosis). Rituximab is under study in a variety of other autoimmune disorders.
Other drugs that target white blood cells are being developed.
Plasma exchange Plateletpheresis (platelet donation) In addition to normal blood donation and transfusion, special procedures are sometimes used. In plateletpheresis, a donor gives only platelets rather than whole blood. Whole blood is drawn from... read more is used to treat a few autoimmune disorders. Blood is withdrawn and filtered to remove abnormal proteins such as autoantibodies. Then the filtered blood is returned to the person.
Intravenous immune globulin (a purified solution of antibodies obtained from volunteer donors and given by vein) is used to treat a few autoimmune disorders. How it works is unknown.