Rationale: Almost half of the patients with anti-neutrophil cytoplasmic antibodies (ANCA) associated small vessel vasculitis relapse and their characteristics are still to be defined

Objective: We aimed to evaluate the relapse rate and its determinants in a cohort of patients with ANCA associated vasculitis with severe kidney involvement.

Methods and results: This is a retrospective study which included 100 patients consecutively admitted in a Nephrology Department with crescentic pauci-immune glomerulonephritis diagnosed by kidney biopsy. ANCAs were assessed by capture ELISA or indirect immunofluorescence (IFI). Patients were followed for a median period of 3.2 [0.1; 5.5] years. The median age was 61.6 years. The clinical condition at presentation was severe (median BVAS 16 and BVAS over 21 in one quarter of patients), mostly because of general, kidney and lung scores. Median creatinine was 5.7 mg/dL and 17% of the patients needed temporary dialysis. Eight patients relapsed (13.8%): one in the lung and seven in the kidney. The median time to relapse was 11.3 [9.2; 19.9] months. None of the investigated parameters allowed for differentiating patients who relapsed from those who did not, except higher hematuria in those who relapsed.

Discussion: In our patients with ANCA vasculitis and severe kidney involvement, the relapse rate is low and hematuria but not ANCA specificity or clinical presentation allows the prediction of relapse.