Although doctors are do not know exactly what causes lupus and other autoimmune diseases, most believe that lupus results from both genetic and environmental stimuli.
Since lupus is known to occur within families, doctors believe that it is possible to inherit a genetic predisposition to lupus. There are no known genes, however, that directly cause the illness. It is probable that having an inherited predisposition for lupus makes the disease more likely only after coming into contact with some environmental trigger.
The higher number of lupus cases in females than in males may indicate that the disease can be triggered by certain hormones. Physicians believe that hormones such as estrogen regulate the progression of the disease because symptoms tend to flare before menstrual periods and/or during pregnancy.
Certain environmental factors have been known to cause lupus symptoms. These include:
Exposure to ultraviolet light, usually from sunlight
Some medications and antibiotics, especially those in the sulfa and penicillin groups
Some infections, such as cytomegalovirus (CMV), parvovirus (such as fifth disease), hepatitis C infections, and the Epstein-Barr virus (in children)
Chemical exposure to compounds such as trichloroethylene in well water and dust