Systemic lupus erythematosus.

Descriptive epidemiologic studies of SLE have been conducted worldwide; the most extensive data are available for Scandinavia, especially Sweden, and the United States. In the United States, blacks have threefold higher incidence, prevalence, and mortality rates compared with whites; the reasons for this excess, however, remain unknown. Analytic and genetic epidemiologic studies suggest a multifactorial etiology of SLE; results support a polygenic mode of inheritance including important roles for an autosomal dominant "autoimmune" gene and female sex hormones. Although a viral etiology remains attractive, there is little evidence to support such a hypothesis. Rather, other environmental factors including chemical exposures may be important as "triggers" of disease. Finally, observational epidemiologic studies demonstrate an increasingly favorable prognosis for patients with SLE, allowing a better understanding of long-term morbidity and impact on overall health status. Future epidemiologic studies should focus on identifying noninfectious environmental etiologic factors and improving the quality of life for all patients with SLE.