Safe Effective Therapy With Low-Dose Glucocorticoid in ANCA-Associated Vasculitis (SAFE-LOW)

* New diagnosis of, or relapse of, granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), consistent with Chapel-Hill consensus definitions * Positive ELISA test for anti-meyloperoxidase (MPO) or anti-proteinase 3 (PR3) * Severe kidney involvement from active AAV, characterised by both of the following: * eGFR \< 40ml/min/1.73m2 (Patients known to have a stable eGFR \<40 ml/min/1.73m2 for \>3 months prior to enrollment are NOT eligible) * Biopsy proven at least focal necrotizing/crescentic glomerulonephritis OR active urinary sediment by microscopy (greater than or equal to 10 red blood cells \[RBC\]/high power field with erythrocyte casts or greater than or equal to 20% dysmorphic RBCs or greater than or equal to 5% acanthocytes without an alternative cause. Exclusion Criteria (any of the following) * A diagnosis of vasculitis other than GPA or MPA (including eosinophilic granulomatosis with polyangiitis, IgA vasculitis, cryoglobulinemic vasculitis, rheumatoid vasculitis) * Positive anti-glomerular basement membrane antibody test or renal biopsy demonstrating linear glomerular immunoglobulin deposition * A diagnosis of systemic lupus erythematosus or Sjögren's syndrome * Receipt of dialysis for \>21 days immediately prior to randomization or prior renal transplant * Age \<18 * Pregnant at time of screening * Treatment with \>1 IV dose of CYC and/or \>14 days PO CYC and/or \>14 days of prednisone/prednisone (less than or equal to 30mg/day) and/or \>1 dose of RTX within the 28 days immediately prior to randomization * Chronic viral infection: HIV. HBV or HCV * Untreated latent mycobacterium tuberculosis infection * Active infection at time of presentation * A comorbidity or condition that, in the opinion of the investigator, precludes the use of GC, CYC or RTX