Serum Uric Acid Associates with Systemic Complement C3 Activation in Severe ANCA-Associated Renal Vasculitides.

Involvement of the complement system is key to the pathogenesis of antineutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis, but immunometabolic implications, especially on serum uric acid (UA) levels, still need to be elucidated. A total of 34 patients with biopsy-proven ANCA-associated renal vasculitis between 2015 and 2020 were retrospectively enrolled. Serum UA levels were correlated with clinical and histopathological characteristics, separated for critically ill (CI, n = 19), myeloperoxidase (MPO)-ANCA ( n = 21) and proteinase 3 (PR3)-ANCA ( n = 13) subgroups. We here identified inverse correlations of serum UA levels and complement C3 levels in the total cohort ( p = 0.005) and the CI subgroup ( p < 0.001). Intrarenal complement C4d deposition in venules correlated with serum UA levels in the total cohort ( p = 0.007) and in the CI subgroup ( p = 0.016). Significant associations of serum UA levels and tubulitis in areas of scarred cortex ( t-IFTA ) were identified in the total cohort ( p = 0.008), and both subgroups of CI ( p = 0.034) and MPO-ANCA ( p = 0.029). In PR3-ANCA, interstitial fibrosis ( ci ) was observed as the strongest association with serum UA levels ( p = 0.022). Our observations broaden our current understanding of contributory metabolic factors that influence the initial disease course in ANCA-associated renal vasculitis.