Causes

Systemic lupus erythematosus is a complex disorder that occurs as a consequence of a number of independent processes and factors.

Environmental factors, such as viruses, exposure to chemicals, or sunlight trigger inflammatory or immune activity. This immune activation may begin as an appropriate response to an unwanted "invader." But, because of a combination of genetic factors, an individual with lupus develops an ongoing immune response that does not shut itself off appropriately. This leads to waxing and waning flares of inflammation that can involve various organs of the body, depending on specific features of this self-perpetuating immune response in individual patients.

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The exact combination of genes that predispose individuals to SLE may differ somewhat from patient to patient, but probably share certain common features which tend to impair the ability of the body to rid itself of immune-triggering particles and which tend to prolong or increase the degree of immune responsiveness to these triggers.

A major characteristic of lupus is that it is an autoimmune response, in which immune factors, called autoantibodies, seem to attack the person's own cells. Some autoantibodies are normal in a well-balanced immune system, and serve various roles to help the body dispose of wastes, protect from invaders that have similarity to human structures, and to keep blood vessels clear. In healthy people, autoantibodies tend to be well-regulated and well "masked," or covered up, until needed. Therefore, it is probably the high activity and high detectability of autoantibodies that makes lupus unique, not the fact that they exist.