Clinical and Pathologic Characteristics of Patients With ANCA-Associated Vasculitis With Renal Arteritis

Background: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by necrotizing inflammation of small vessels, typically affecting glomerular capillaries. However, small arteries can also be affected. The clinical significance of this subgroup of patients remains unclear. This study aimed to analyze the clinicopathologic features and prognostic significance of renal arteritis in Chinese patients with AAV. Methods: A large multicenter cohort of 511 patients with renal biopsy-proven AAV, diagnosed between 2002 and 2023, was retrospectively enrolled. Clinicopathologic parameters were compared between those with and without renal arteritis (termed AAV_A+ and AAV_A-, respectively). The prognostic value of renal arteritis was further analyzed. Results: Among the 511 patients with AAV, 73 (14.3%) had renal arteritis. Compared with patients with AAV_A-, patients with AAV_A+ were significantly older at diagnosis, with more pronounced systemic inflammation and more frequent extrarenal involvement. Although baseline renal function was comparable, patients with AAV_A+ exhibited a distinct histopathologic phenotype, with fewer crescentic lesions but more inflammatory and necrotizing injuries. Despite patients with AAV_A+ showed a better response to immunosuppressive therapy, renal survival was similar between the 2 groups. However, among patients classified as low or moderate risk by the ANCA kidney risk score (AKRiS), renal survival was significantly worse in patients with AAV_A+. For this subgroup, renal arteritis was independently associated with an increased risk of end-stage kidney disease (ESKD). Conclusion: AAV with renal arteritis represents a distinct clinical and pathologic phenotype in the Chinese population. In patients classified as low or moderate risk by the AKRiS, renal arteritis was independently associated with an increased risk of ESKD.