Background Microscopic polyangiitis (MPA) is a common form of ANCA associated vasculitis in Japan. Renal involvement is frequent in MPA and an important factor with respect to therapeutic methods and outcomes.

Objectives To determine the association between renal characteristics at diagnosis and the relapse.

Methods A retrospective review was conducted in 28 patients who were newly diagnosed as MPA. (January 2007 to August 2015) Baseline characteristics are collected include urine profile and renal pathology. The primary endpoint is the first flare. Disease flare is defined an increase in at least one major Birmingham vasculitis activity score (BVAS) items. Furthermore, analysis on other outcomes, such as end stage renal failure, induction of hemodialysis and death has been conducted.

Results Of the 28 patients with MPA, all patients had renal vasculitis. 18 achieved BVAS remission, and relapse occurred among 5 patients (19.2%). Cox multivariate analysis showed that amount of proteinuria on admission was a predictor of relapse (HR 4.2; 95% CI, 0.13–10.5). In renal biopsy, those relapsed five cases tend to have more intensive glomerulonephritis, according to the European Vasculitis Study Group (EUVAS) classification, though no statistical significance was performed.

Conclusions Amount of proteinuria is a risk factor for relapse in MPA.

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Disclosure of Interest None declared