Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body attacks its own cells. Autoimmune diseases are a major cause of immune-mediated diseases.
Today there are more than 40 human diseases classified as either definite or probable autoimmune diseases, and they affect 5% to 7% of the population. Almost all autoimmune diseases appear without warning or apparent cause, and most patients suffer from fatigue.
The causes of autoimmune diseases are still obscure: Some are thought to be either examples of or precipitated by diseases of affluence. For example, arthritis and obesity are acknowledged to be related, and the World Health Organisation states that arthritis is most common in developed countries. Most autoimmune diseases are probably the result of multiple circumstances, for example, a genetic predisposition triggered by an infection.
Women tend to be affected more often by autoimmune disorders; nearly 79% of autoimmune disease patients in the USA are women. Also they tend to appear during or shortly after puberty. It is not known why this is the case, although hormone levels have been shown to affect the severity of some autoimmune diseases such as multiple sclerosis. Other causes may include the presence of fetal cells in the maternal bloodstream. 
Diseases with a complete or partial autoimmune etiology:
The "Mesh" column lists those conditions that are classified as autoimmune by the MeSH system.
is an acquired immune-mediated inflammatory disorder of the peripheral nervous system (i.e., not the brain and spinal column). It is also called acute inflammatory demyelinating polyneuropathy, acute idiopathic polyradiculoneuritis, acute idiopathic polyneuritis and Landry's ascending paralysis.
is a chronic (long-lasting) autoimmune disease wherein the immune system, for unknown reasons, becomes hyperactive and attacks normal tissue. This attack results in inflammation and brings about symptoms. This is a "Non-organ-specific" type of autoimmune disease.
is a neurological disorder that appears to the result of an autoimmune attack on the nervous system. Symptoms include opsoclonus, myoclonus, ataxia, intention tremor, dysphasia, dysarthria, mutism, hypotonia, lethargy, irritability or malaise. About half of all OMS cases occur in association with neuroblastoma.
appears to be an autoimmune disease that affects the biliary epithelial cells (BECs) of the small bile duct in the liver. Although the cause is yet to be determined, most of the patients (>90%) appear to have auto-mitochondrial antibodies (AMAs) against pyruvate dehydrogenase complex (PDC), an enzyme that is found in the mitochondria.
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