Systemic Lupus Erythematosus: Overview and Risk Factors  

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder of uncertain etiology. Various immune changes occur, including B cell lymphocyte hyperreactivity, T cell lymphocyte defects, complement activation, and autoantibodies to nuclear and cellular antigens.

The clinical course is irregular, with periods of exacerbation and remission, and the severity of disease ranges from mild to life–threatening. Virtually any organ system of the body can be involved, most notably the skin, joints, kidneys, lungs, nervous system, and serous membranes. Organ damage results from deposition of immune complexes within tissues and autoantibody–mediated destruction of host cells. The most common clinical presentations are skin changes, arthritis, and constitutional symptoms (fever, fatigue, weight loss). But more serious manifestations are not uncommon, such as vasculitis (including of the central nervous system), nephritis, pleuritis, pericarditis, arterial and venous thromboses, anemia, leukopenia, and thrombocytopenia.

Risk Factors

The prevalence of SLE is 40 to 50 cases per 100,000 people. Incidence has tripled over the past half–century, but this is probably due mostly to improved detection of mild cases.  

• Gender. Nearly 90% of cases occur in women, particularly during the childbearing years. The female–to–male ratio is 3:1 in children, approximately 15:1 in adults, and 8:1 in postmenopausal women.
• Ethnicity. African Americans are most commonly affected and are 3 times more likely to have SLE than Caucasians. Hispanic, Asian, and Native Americans also have an increased incidence compared with Caucasians.
• Geography. Prevalence varies significantly by geography. For example, SLE is rare in West Africa, increases in frequency in Central and Southern Africa, and has a high frequency in America and Europe. It is unclear whether this variation is related to environmental or genetic factors.
• Age. Peak onset occurs between 20 and 50 years of age.
• Genetics. There is an increased incidence in close relatives (SLE affects approximately 10% of relatives of index patients) and a strong correlation in monozygotic twins, but specific involved genes have yet to be determined.
• Medications. Development of SLE has been associated with use of hydralazine, isoniazid, methyldopa, and procainamide. However, clinical manifestations of drug–induced SLE tend to be less severe and often remit with removal of the offending agent.