In an autoimmune disorder, antibodies or cells produced by the body attack the body's own tissues (see Autoimmune Disorders). Many autoimmune disorders affect connective tissue in a variety of organs. Connective tissue is the structural tissue that gives strength to joints, tendons, ligaments, and blood vessels (see Biology of the Musculoskeletal System: Introduction).

In autoimmune disorders, inflammation and the immune response may result in connective tissue damage, not only in and around joints but also in other tissues, including vital organs, such as the kidneys and organs in the gastrointestinal tract. The sac that surrounds the heart (pericardium), the membrane that covers the lungs (pleura), and even the brain can be affected. The type and severity of symptoms depend on which organs are affected.

An autoimmune disorder of connective tissue is diagnosed on the basis of its particular symptom pattern, the findings during a physical examination, and the results of laboratory tests. Sometimes the symptoms of one disease overlap with those of another so much that doctors cannot make a distinction. In this case, the disorder may be called undifferentiated connective tissue disease or an overlap disease.

Last full review/revision February 2008 by Rula A. Hajj-Ali, MD