Treatment of patients with PR3-ANCA-associated vasculitis consists of two phases: remission induction with highly effective, but also relatively toxic, drugs and, secondly, after remission is achieved, maintenance therapy with less toxic drugs. Currently, remission-maintenance therapy with azathioprine is stopped after approximately 18 months. However, the optimal duration of azathioprine maintenance therapy is unknown.~The investigators have found that patients with PR3-ANCA-associated vasculitis who remain C-ANCA positive after induction of remission have an increased risk to experience relapse of disease (MC Slot et al. Arthritis Rheum. 2004 15;51(2):269-73). Therefore they will test whether relapse risk in these patients can be reduced by extending maintenance therapy at the cost of acceptable therapy related toxicity. After induction of stable remission, ANCA will be measured by IIF. C-ANCA positive patients will be randomized for either standard therapy with azathioprine (until 18 months after diagnosis), or longterm azathioprine maintenance therapy (until 48 months after diagnosis).
Treatment of patients with PR3-ANCA-associated vasculitis consists of two phases: remission induction with highly effective, but also relatively toxic, drugs and, secondly, after remission is achieved, maintenance therapy with less toxic drugs. Currently, remission-maintenance therapy with azathioprine is stopped after approximately 18 months. However, the optimal duration of azathioprine maintenance therapy is unknown.~The investigators have found that patients with PR3-ANCA-associated vasculitis who remain cytoplasmic anti-neutrophil cytoplasmic autoantibody (C-ANCA) positive after induction of remission have an increased risk to experience relapse of disease. Therefore they will test whether relapse risk in these patients can be reduced by extending maintenance therapy at the cost of acceptable therapy related toxicity. After induction of stable remission, ANCA will be measured by immunofluorescence (IIF). C-ANCA positive patients will be randomized for either standard therapy with azathioprine (until 18 months after diagnosis), or longterm azathioprine maintenance therapy (until 48 months after diagnosis).