Objectives To describe characteristics, treatment, and outcome of isolated antineutrophil cytoplasm antibody (ANCA)-associated scleritis at diagnosis, in comparison with idiopathic scleritis with negative ANCA tests. Methods This retrospective case control multicentre study was performed within the French Vasculitis Study Group (FVSG) network and in three French tertiary ophthalmologic centres. Data of patients with scleritis without any systemic manifestation and with positive ANCA results were compared to those of a control group of patients with idiopathic scleritis with negative ANCA tests. Results 120 patients, including 38 patients with ANCA-associated scleritis and 82 control patients, diagnosed between January 2007 and April 2022, were included. Median follow-up was 28 months (IQR 10–60). Median age at diagnosis was 48 (IQR 33–60) and 75% were female subjects. Scleromalacia was more frequent in ANCA-positive patients (p = 0.027). 54% had associated ophthalmologic manifestations, without significant differences. ANCA-associated scleritis more frequently required systemic medications, including glucocorticoids (76% versus 34%, p < 0.001), and rituximab (p = 0.03), and had a lower remission rate after the first- and second-line treatment. Systemic AAV occurred in 30.7% of patients with PR3- or MPO-ANCA, after a median interval of 30 months (IQR: 16.3; 44). Increased CRP >5 mg/L at diagnosis was the only significant risk factor of progression to systemic AAV (adjusted HR 5.85; 95%CI 1.10–31.01; p = 0.038). Conclusion Isolated ANCA-associated scleritis are mostly anterior scleritis with higher risk of scleromalacia than ANCA-negative idiopathic scleritis and are more often difficult-to-treat. One third of patients with PR3- or MPO-ANCA scleritis progressed to systemic AAV.

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