Systemic Lupus Erythematosus (SLE) is a chronic, remitting and relapsing, multisystem autoimmune disease affects predominantly women, with an incidence of 1 in 700 among women between the ages of 20 and 60 years, about 1 in 250 among black women, and 10:1 female to male ratio. The clinical features of SLE is so variable that the American College of Rheumatology has established criteria for diagnosis of this disorder.

The cause of SLE remains unknown, but the existence of a seemingly limitless number of antibodies in these patients against self-constituents indicates that the fundamental defect in SLE is a failure of the mechanism that maintain self-tolerance.

Many different autoantibodies are found in patients with SLE. The most frequent are antinuclear, particularly anti DNA antibodies, others include antibodies against ribonucleoprotein, histone and nucleolar antigens. Immune complexes formed from these autoantibodies and their specific antigens are responsible for glomerulonephritis, arthritis, and vasculitis. Hemolytic anemia and thrombocytopenia are due to autoantibodies against erythrocytes and platelets, respectively.

SLE is a complex genetic trait with contribution from MHC and multiple non-MHC genes. Family members of patients have an increased risk of developing SLE. There is a higher rate of concordance (>20%) in monozygotic twins when compared with dizygotic twins (1%-3%).

There are many indications that, in addition to genetic factors, several environmental or non genetic factors must be involved in the pathogenesis of SLE. Drugs such as hydralazine, procainamide, and D-penicilamine can induce an SLE-like response in human. Exposure to ultraviolet light may cause exacerbation of the disease in many individuals. Sex hormones seem to exert an important influence on the occurrence and manifestation of SLE. During the reproductive years, the frequency of SLE is 10 times greater in women than in men, and exacerbation has been noted during normal menses and pregnancy.