Relative to studies of systemic lupus erythematosus (SLE), epidemiologic studies of chronic cutaneous lupus erythematosus (CCLE) are rare and are limited to populations with no racial diversity. We sought to provide minimum estimates of the incidence of primary CCLE (CCLE in the absence of SLE) in a population comprised predominantly of white individuals and black individuals in the southeastern region of the US.
The Georgia Lupus Registry allowed for the use of multiple sources for case-finding, including dermatology and rheumatology practices, multispecialty health care facilities, and dermatopathology reports. Cases with a clinical or clinical/histologic diagnosis of CCLE were classified as definite. Cases ascertained exclusively from dermatopathology reports were categorized as probable. Age-standardized incidence rates stratified by sex and race were calculated for discoid lupus erythematosus (DLE) in particular and for CCLE in general.
The overall age-adjusted estimates for combined (definite and probable) CCLE were 3.9 per 100,000 person-years (95% confidence interval [95% CI] 3.4-4.5). The overall age-adjusted incidences of definite and combined DLE were 2.9 (95% CI 2.4-3.4) and 3.7 (95% CI 3.2-4.3) per 100,000 person-years, respectively. When capture-recapture methods were used, the age-adjusted incidence of definite DLE increased to 4.0 (95% CI 3.2-4.3). The black:white and female:male incidence ratios for definite DLE were 5.4 and 3.1, respectively.
Our findings underscore the striking racial disparities in susceptibility to primary CCLE, with black individuals having a 3-fold to 5-fold increased incidence of CCLE in general, and DLE in particular, compared with white individuals. The observed sex differences were consistent with those reported previously, with a 3 times higher risk of DLE in women compared with men.