No one knows the root cause of this disease. It has a long history, but only in the last half century has serious research been done to better understand the origins of lupus. Most research indicates that patients are predisposed (your body had all the “right” ingredients to make the disease) to lupus and a catalytic event (something emotionally or physically stressful) triggers the onset of the disease.

The cause(s) of lupus is unknown, but environmental and genetic factors are involved. While scientists believe there is a genetic predisposition to the disease, it is known that environmental factors also play a critical role in triggering lupus. Some of the environmental factors that may trigger the disease are infections, antibiotics (especially those in the sulfa and penicillin groups), ultraviolet light, extreme stress, and certain drugs.

Although lupus is known to occur within families, there is no known gene or genes which are thought to cause the illness. Only 10 percent of lupus patients will have a close relative (parent or sibling) who already has or may develop lupus. Statistics show that only about 5% of the children born to individuals with lupus will develop the illness.

Lupus is often called a "woman's disease" despite the fact that many men are affected. Lupus can occur at any age, and in either sex, although it occurs more frequently among adult females than among adult males (nine out of ten diagnosed are female). The symptoms of the disease are the same in men and women. Women of African, Native American, and Asian origin are thought to develop the disease more frequently than Caucasian women.

Hormonal factors may explain why lupus occurs more frequently in females than in males. The
increases of disease symptoms before menstrual periods and/or during pregnancy support the belief
that hormones, particularly estrogen, may be involved. However, the exact hormonal reason for the greater prevalence of lupus in women, and the cyclic increase in symptoms, is unknown.

Source: National Institute of Health