- Predilection for females of childbearing age.
- Multisystem disease, often with a relapsing-remitting course.
- Photosensitive rash, polyarthritis, serositis, and fatigue are common manifestations of disease flares.
- Renal disease and central nervous system involvement are important causes of morbidity.
- Presence of antinuclear antibodies.
- Certain autoantibodies (anti-dsDNA and anti-Sm) have great specificity for the diagnosis of SLE, but lack sensitivity.
- Hypocomplementemia may occur during flares.
Systemic lupus erythematosus (SLE) is the prototypic autoimmune disease characterized by multisystem involvement and the production of an array of autoantibodies. Clinical features in individual patients are highly variable, ranging from skin and joint involvement to organ-threatening and life-threatening disease. SLE is typically associated with a waxing and waning clinical course, but some patients have continuous disease activity.
The prevalence of SLE varies across gender, race/ethnicity, and geographic regions. SLE demonstrates a striking female predominance with a peak incidence of disease during the reproductive years. In adults, the female to male ratio is 10–15:1. In the United States, the estimated prevalence is 100 per 100,000 white women and 400 per 100,000 black women. SLE is more common in blacks in the United States but is rare among blacks in Africa. Approximately 160,000 to 320,000 people in the United States are living with SLE.
Although the etiology of SLE remains unclear, genetic, hormonal, and environmental influences play a role in disease pathogenesis. It is postulated that an environmental exposure triggers the onset of disease in a genetically susceptible person. Evidence of a genetic component to SLE is derived from studies showing strong familial risk. The disease concordance rate of 24–58% for monozygotic twins in comparison to the concordance rate of 2–5% for dizygotic twins confirms this strong genetic component. Multiple genes have been associated with SLE, including the genes within the major histocompatibility complex and genes that encode components of the complement pathway, Fcγ receptors, protein tyrosine phosphatase non-receptor type 22 (PTPN22), programmed cell death 1 gene (PDCD1), and cytotoxic T lymphocyte associated antigen 4 (CTLA4). The reasons for female sex predilection remain murky. Some observational data suggest that sex hormones might contribute to disease onset. For example, data from the Nurses Health Study suggest that early age at menarche (relative risk 2.1), oral contraceptive use (relative risk 1.5), and use of postmenopausal hormones (relative risk 1.9) increases the risk of SLE. In addition, the risk of SLE in men with Klinefelter syndrome (47, XXY) is 14-fold higher than in healthy male controls. In contrast, large controlled trials have shown that combined oral contraceptives do not increase the risk of flares in women with stable SLE, and studies examining serum sex hormone levels in patients with lupus compared with patients in a control group have been inconclusive. Thus, whether hormonal factors or nonhormonal aspects of sex are most important in influencing disease risk remains to be determined.
Various environmental factors have been examined as potential triggers for the development of SLE. Smoking is a ...