Prevalence and Risk Factors of Systemic Lupus Erythematosus in Patients With Chronic Cutaneous Lupus: A Bicentric Study Employing Three Classification Criteria

Abstract

BACKGROUND: Chronic cutaneous lupus erythematosus (CCLE) is the most common form of cutaneous lupus erythematosus, accounting for about 80% of cases. While patients with CCLE can develop systemic lupus erythematosus (SLE), the prevalence and risk factors of this association remain poorly studied, especially in North African populations. METHODS: We conducted a bicentric study including all patients with histologically confirmed CCLE in two tertiary referral hospitals in Tunis between 2013 and 2023. SLE was classified using three criteria sets: ACR 1997, SLICC 2012, and ACR/EULAR 2019. Univariate and multivariate analyses were performed. RESULTS: Ninety-five patients with CCLE (median age 48 years, 75% female) were included. The prevalence of SLE varied significantly depending on the classification criteria used: 24% with ACR 1997, 32% with SLICC 2012, and 21% with ACR/EULAR 2019. Independent risk factors for SLE included arthralgias consistently across all classification criteria. Other risk factors for SLE differed among classification systems. For instance, asthenia and elevated ESR were independent risk factors under the ACR 1997 criteria, while female sex and extensive skin involvement were unique to the SLICC 2012 criteria. CONCLUSIONS: This study, the largest in North Africa aiming to identify the prevalence and risk factors of SLE among CCLE patients, showed significant variability depending on the used classification criteria. Arthralgias represented an independent risk factor for SLE in CCLE patients. The findings of this study were used to develop a diagnostic algorithm to assist clinicians.