Reappraisal of renal arteritis in anca-associated vasculitis: Clinical characteristics, pathology, and outcome

Background: Renal involvement inANCA-associated vasculitis (AAV) is associated with poor outcomes. The clinical significance of arteritis of the small kidney arteries has not been evaluated in detail.

Methods: In a multicenter cohort of patientswith AAV and renal involvement,we sought to describe the clinicopathologic characteristics of patientswith AAVwho had renal arteritis at diagnosis, and to retrospectively analyze their prognostic value.

Results: We included 251 patients diagnosed with AAV and renal involvement between 2000 and 2019, including 34 patients (13.5%) with arteritis. Patients with AAV-associated arteritis were older, and had a more pronounced inflammatory syndrome compared with patients without arteritis; they also had significantly lower renal survival (P50.01). Inmultivariable analysis, theANCA renal risk score, age at diagnosis, history of diabetesmellitus, and arteritis on index kidney biopsywere independently associatedwith ESKD. The addition of the arteritis status significantly improved the discrimination of the ANCA renal risk score, with a concordance index (C-index) of 0.77 for the ANCA renal risk score alone, versus a C-index of 0.80 for the ANCA renal risk score plus arteritis status (P50.008); ESKD-free survival was significantly worse for patients with an arteritis involving small arteries who were classified as having low or moderate risk, according to the ANCA renal risk score. In two external validation cohorts, we confirmed the incidence and phenotype of this AAV subtype.

Conclusions: Our findings suggestAAVwith renal arteritis represents adifferent subtype ofAAVwith specific clinical and histologic characteristics. The prognostic contribution of the arteritis status remains to be prospectively confirmed.