What are autoimmune diseases?
When the immune system functions normally, it produces a response intended to protect against harmful or foreign substances like bacteria, parasites, and cancerous cells. The response may include specific immune cells and/or antibodies. Autoimmune diseases arise when the immune system attacks one or more of the body's normal constituents as if they were invaders. When the immune system fails to recognize "self" it may produce immune cells or antibodies (called autoantibodies) that target its own cells, tissues, and/or organs. Those attacks cause inflammation and tissue damage that lead to autoimmune disorders.
There are over 80 diseases that occur as a result of autoimmune responses. The National Institutes of Health (NIH) estimates that 23.5 million Americans are affected. Most autoimmune disorders are rare. However, the overall number of cases of autoimmune diseases is rising for unknown reasons. Women are disproportionately affected, representing 80% of people with autoimmune diseases. Some diseases such as lupus and Hashimoto thyroiditis affect 9-10 women for every man affected.
The cause of most autoimmune diseases is unknown, but it appears that there is an inherited predisposition in many cases. In a few types of autoimmune disease (such as rheumatic fever), a virus or infection with bacteria triggers an immune response and the antibodies or immune cells called T-cells attack normal cells because some part of their structure resembles a part of the infecting microorganism.
Autoimmune disorders fall into two general types: those that damage many organs (systemic autoimmune diseases) and those where only a single organ or tissue is directly damaged by the autoimmune process (localized). However, the distinctions become blurred as the effect of localized autoimmune disorders frequently extends beyond the targeted tissues, indirectly affecting other body organs and systems.
In some cases, the antibodies may not be directed at a specific tissue or organ. For example, antiphospholipid antibodies can react with substances (phospholipids) that are the normal constituents of platelets and the outermost layer of cells (cell membranes). This reaction can lead to the inappropriate formation of blood clots within blood vessels (thrombosis).
Autoimmune disorders can be difficult to recognize and diagnose. Autoimmune disorders affecting multiple organs can lead to highly variable signs and symptoms that can change in severity over time. Vague and slow to develop signs and symptoms may be present and can be misleading during diagnosis. Some of the more common symptoms of autoimmune disorders include fatigue, general feeling of being unwell (malaise), dizziness, joint pain, rash, and low grade fever.
Laboratory tests performed to diagnose autoimmune disorders depend on the particular disorder the health practitioner suspects a person has but usually include blood tests for one or more autoantibodies as well as tests for inflammation such as CRP and ESR.
Some examples of autoimmune disorders are listed on the next page.