An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues.
What triggers an autoimmune disorder 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 medications that suppress the activity of the immune system.
(See also Overview of Allergic Reactions.)
The immune system must first recognize 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.
When certain white blood cells (B cells and T cells) encounter an antigen, they learn how to attack it and thus defend the body from the potentially dangerous antigen. B cells produce antibodies, which are one of the body's main immune defenses against antigens. Antibodies tightly bind to a specific antigen and tag it for attack or directly neutralize it. The body produces thousands of different antibodies. Each antibody is specific to a particular antigen. Cells of the immune system remember the specific antigen so that they can attack it even more efficiently the next time they encounter it.
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 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, rheumatoid arthritis, Hashimoto thyroiditis, type 1 diabetes mellitus, systemic lupus erythematosus (lupus), and vasculitis. Additional disorders that are believed to be autoimmune include Addison disease, polymyositis, Sjögren syndrome, progressive systemic sclerosis, many cases of glomerulonephritis (inflammation of the kidneys), and some cases of infertility.
Some Autoimmune Disorders
Disorder | Main Tissues Affected | Consequences |
|---|---|---|
Red blood cells | Anemia (decreased number of red blood cells) develops, causing fatigue, weakness, and light-headedness. The spleen may enlarge. The anemia can be severe and even fatal. | |
Skin | Large blisters, surrounded by red, swollen areas, form on the skin. Itching is common. The disorder affects mainly older adults and can be life threatening, especially in older adults who have other disorders. | |
Beta cells of the pancreas (which produce insulin) | Symptoms may include excessive thirst, urination, and appetite, as well as various long-term complications. insulin. The prognosis varies greatly and tends to be worse when the disease is severe and lasts a long time. | |
Lungs and kidneys | Symptoms, such as shortness of breath, coughing up blood, fatigue, and swelling, may develop. The prognosis is good if treatment begins before severe lung or kidney damage occurs. | |
Thyroid gland | The thyroid gland is stimulated and enlarged, resulting in high levels of thyroid hormones (hyperthyroidism). Symptoms may include a rapid heart rate, intolerance of heat, tremor, weight loss, and nervousness. With treatment, the prognosis is good. | |
Thyroid gland | The thyroid gland is inflamed and damaged, resulting in low levels of thyroid hormones (hypothyroidism). Symptoms may include weight gain, coarse skin, intolerance of cold, and drowsiness. Lifelong treatment with thyroid hormone is necessary and usually relieves the symptoms completely. | |
Brain and spinal cord | The tissue that covers affected nerve cells is damaged. As a result, the cells cannot conduct nerve signals normally. Symptoms may include weakness, abnormal sensations, vertigo, problems with vision, muscle spasms, and incontinence. Symptoms vary over time and may come and go. The prognosis varies. | |
The connection between nerves and muscles (neuromuscular junction) | Muscles, particularly those of the eyes, weaken and tire easily, but the weakness varies in intensity. The pattern of progression varies widely. Medications can usually control the symptoms. | |
Skin | Large blisters form on the skin and mucous membranes (such as those lining of the mouth). The disorder can be life threatening if untreated. | |
Certain cells in the stomach's lining | Damage to cells in the stomach's lining makes absorbing vitamin B12 difficult. (Vitamin B12 is necessary for the production of mature blood cells and the maintenance of nerve cells.) Anemia results, often causing fatigue, weakness, and light-headedness. Nerves can be damaged, resulting in weakness and loss of sensation. Without treatment, the spinal cord may be damaged, eventually contributing to loss of sensation, weakness, and incontinence. The risk of stomach cancer is increased. Otherwise, with treatment, the prognosis is good. | |
Joints or other tissues, such as lung, nerve, skin, and heart tissue | Many symptoms are possible. They include fever, fatigue, joint pain, joint stiffness, deformed joints, shortness of breath, loss of sensation, weakness, rashes, chest pain, and swollen joints and tendons. The prognosis varies. | |
Systemic lupus erythematosus (lupus) | Joints, kidneys, skin, lungs, heart, brain, and blood cells | The joints, although inflamed, do not become deformed. Symptoms of anemia, such as fatigue, weakness, and light-headedness, and those of kidney, lung, or heart disorders, such as fatigue, shortness of breath, itching, and chest pain, may occur. A rash may develop. Hair loss is common. The prognosis varies widely, but most people can lead an active life despite occasional flare-ups of lupus. |
Blood vessels | Vasculitis can affect blood vessels in one part of the body (such as the nerves, head, skin, kidneys, lungs, or intestine) or several parts. There are several types. Symptoms (such as rashes, abdominal pain, weight loss, difficulty breathing, cough, chest pain, headache, loss of vision, and symptoms of nerve damage or kidney failure) depend on which part of the body is affected. The prognosis depends on the cause and how much tissue is damaged. Usually, the prognosis is much better with treatment. |
Causes of Autoimmune Disorders
Autoimmune reactions can be triggered in several ways:
A normal body substance is altered, for example, by a virus, a medication, sunlight, or radiation. The altered substance may then 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.
T cells, another type of white blood cell that are involved in the immune response, may also malfunction and damage 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 of Autoimmune Disorders
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.
Diagnosis of Autoimmune Disorders
Blood tests
Doctors suspect an autoimmune disorder based on a person's symptoms. To help confirm the diagnosis, doctors do several laboratory tests.
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.
C-Reactive protein (CRP): This test also measures overall inflammation. CRP is a protein released by the liver in times of inflammation such as active autoimmune disease.
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
Antinuclear antibodies, which are typically present in systemic lupus erythematosus
Rheumatoid factor or anti-cyclic citrullinated peptide (anti-CCP) antibodies, which are typically present in rheumatoid arthritis
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 determine whether an autoimmune disorder is present.
Did You Know...
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Treatment of Autoimmune Disorders
Medications that suppress the immune system, including corticosteroids
For some autoimmune disorders, plasma exchange and intravenous immune globulin
Medication treatment
Medications that suppress the immune system
Often, corticosteroids
Certain autoimmune disorders (such as multiple sclerosis and thyroid disorders) are also treated with medications other than immunosuppressants and corticosteroids. Treatment to relieve symptoms may also be needed.
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 medications can also increase the risk of infection and certain skin cancers.
Certain medications specifically target white blood cells. White blood cells help defend the body against infection but also participate in autoimmune reactions. These medications include the following:
blocks the activation of one kind of white blood cell (T cell) and is used in rheumatoid arthritis.
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), including granulomatosis with polyangiitis
Other medications that target white blood cells are being developed.
Plasma exchange and intravenous immune globulin
Plasma exchange 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.
Prognosis for Autoimmune Disorders
Some autoimmune disorders resolve as inexplicably as they began. However, most autoimmune disorders are chronic. Medications are often required throughout life to control symptoms.
The prognosis varies depending on the disorder.
