Epidemiology of Isolated Cutaneous Lupus Erythematosus in the Multiethnic Population of Reunion Island: A Retrospective Multicenter Study.

Objective: Few data are available about the epidemiology of cutaneous lupus erythematosus (CLE) in the Southern hemisphere and in multiethnic populations. We describe the prevalence, incidence, and clinical characteristics of isolated CLE in the multiethnic population of Reunion Island, France, including patients with dark skin.

Methods: The study was performed in all public hospitals and private dermatology practices in Reunion Island. Cases were identified through informatics databases. Cases were defined as isolated CLE, meaning they did not fulfill the criteria for systemic lupus erythematosus (SLE). Incident cases were collected from 2008 to 2021. Prevalence was calculated on January 1, 2022. A capture-recapture analysis was performed to estimate both prevalence and incidence.

Results: A total of 268 cases of CLE were identified and 218 were incident cases. The standardized prevalence of CLE was 43 out of 100,000 persons and the average annual standardized incidence was 3.1 per 100,000 person-years (PY). With a capture-recapture analysis, prevalence and annual incidence were estimated to be 99 out of 100,000 persons (95% CI 77.10-136.45) and 5.7 per 100,000 PY (95% CI 4.40-7.95), respectively. The mean age at diagnosis was 41.7 years and the ratio of female to male individuals was 4:1. Patients with dark skin had a higher rate of discoid CLE and were more likely to receive immunosuppressants. Generalized discoid CLE, panniculitis, and overlapping subtypes of CLE appeared as predictive markers of progression toward SLE.

Conclusion: The prevalence and incidence of CLE in the multiethnic population of Reunion Island seem higher than in light-skinned populations. We highlight new risk factors of evolution toward SLE that should be known by practitioners to adjust follow-up.