Patients with newly diagnosed or relapsing granulomatosis with polyangiitis , microscopic polyangiitis , or renal-limited ANCA-associated vasculitis in complete remission after a cyclophosphamide-glucocorticoid regimen were randomly assigned to receive either 500 mg of rituximab on days 0 and 14 and at months 6 , 12 , and 18 after study entry or daily azathioprine until month 22 .