Renal involvement at baseline can predict major renal relapse in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis.

In ANCA-associated vasculitis (AAV), renal relapses are cause of concern as they are unpredictable and predictors of end-stage renal disease (ESRD). We aimed to assess the frequency of major renal (MR) relapses in AAV and to identify independent base-line predictors. We performed a retrospective monocentric observational cohort study of patients affected by granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and renal limited vasculitis (RLV), diagnosed from 2000 to 2019, and who achieved clinical remission defined as Birmingham Vasculitis Activity Index version 3 (BVASv3)=0 and/or clinical judgment. MR relapse was defined as the occurrence of major items of renal BVASv3. Univariate and multivariable analysis was performed with competitive risk analysis. We included 96 patients: 73 GPA, 21 MPA and 2 RLV. Eighty-five (90%) patients were ANCA-positive: 56 c-ANCA/PR3, 28 p-ANCA/MPO and 1 double positive. During the follow-up, 17/96 patients developed at least one MR relapse, 2/96 progressed to ESRD and 3/96 died without events; 74 did not develop MR relapse. Patients with MR relapse were all ANCA positive and had higher frequency of skin (p=0.034), kidney (p=0.004) and nervous system (p=0.024) involvement and lower fre¬quency of ear, nose and throat (ENT) manifestations (p=0.043). At multivariable analysis, renal involvement at baseline (sHR 20.4, 95% confidence interval (95% CI) 2.6-158.2, p=0.004) and remission-induction treatment without cyclophosphamide and/or rituximab (sHR 4.2, 95% CI 1.5-12.0, p=0.007) were independent predictors of MR relapses. Baseline renal involvement predicts MR relapse in AAV while intense initial treatment seems to be protective.