Ethnic differences in the epidemiology of cutaneous lupus erythematosus in New Zealand

Abstract

Background The prevalence and variation by ethnicity of cutaneous lupus in New Zealand is not known. Therefore, a cross-sectional study to determine the prevalence and variation by ethnicity of cutaneous lupus in the ethnically diverse community of South Auckland, New Zealand, was undertaken. Methods Multiple sources were examined to determine the prevalence of acute cutaneous lupus erythematosus, subacute cutaneous erythematosus and discoid lupus erythematosus. Ethnicities examined were European, Māori/Pacific and Indian/Asian. Capture–recapture was used to determine the overall population prevalence of cutaneous lupus. Results A total of 145 cases of cutaneous lupus were identified. There were 22 men and 123 women, with an average age (standard deviation), respectively, of 46.4 (±21.5) and 43.1 (±14.8) years. There were 53 cases of acute cutaneous lupus erythematosus, 19 cases of subacute cutaneous erythematosus and 66 cases of discoid lupus erythematosus. The age and sex adjusted relative risk (95% confidence interval; CI) of Māori/Pacific compared to the European population was 2.47 (95% CI 1.67–3.67) for all types of cutaneous lupus, 1.60 (95% CI 0.84–3.18) for acute cutaneous lupus erythematosus, 0.09 (95% CI 0.01–1.1) for subacute cutaneous erythematosus and 5.96 (95% CI 3.06–11.6) for discoid lupus erythematosus. The overall prevalence of cutaneous lupus was 30.1 (95% CI 25.5–35.4) per 100,000. However, capture–recapture estimated the unadjusted prevalence of cutaneous lupus to be 86.0 (95% CI 78.1–94.7) per 100,000. Conclusion Māori and Pacific people in Auckland, New Zealand, have a greater relative risk of all types of cutaneous lupus compared to the European population and a particularly high risk of discoid lupus erythematosus.