Prevalence and clinical associations of ultrasound-confirmed enthesitis in systemic lupus erythematosus

Objectives: To assess the prevalence of ultrasound (US)-confirmed enthesitis in a cohort of patients with systemic lupus erythematosus (SLE) and to analyze the clinical associations to enthesitis during the course of SLE. Methods: In a retrospective analysis of the SLE cohort of the Lupus Unit of the Careggi University Hospital, US examinations of SLE patients presenting with tender and/or swollen joints were retrieved to assess the presence of enthesitis. Patients with US-proven enthesitis were compared with SLE controls with tender and/or swollen joints who showed no US-evidence of enthesitis. Clinical and laboratory features were compared at disease onset and during follow-up. Results: A total of 400 patients fulfilling EULAR/ACR classification criteria for SLE were assessed. Of them, 106 underwent articular US examination. Evidence of enthesitis was found in 31/106 (29.2%) patients. Seventy-one patients without US-enthesitis were included as controls, 4 were excluded due to lack of follow-up data. Laboratory and clinical features were comparable between cases and controls at disease onset. Throughout a median follow-up of 10.0 (IQR 8.3-23.3) years for cases and 12.4 (IQR 7.2-13.3) years for controls, patients with enthesitis were less likely to develop renal involvement (22.6% vs 46.5%, p= 0.028) and failed B cell depletion more frequently (75.0% vs 0%). Conclusion: In SLE patients with clinically active joints, US-proven enthesitis is a fairly common finding. Enthesitis in SLE could be the hallmark of a distinct disease phenotype with less renal involvement, more arthritis, and low response to anti-CD 20 therapy, potentially requiring a tailored treatment.