ANCA: antineutrophil cytoplasmic antibody; GPA: granulomatosis with polyangiitis; MPA: microscopic polyangiitis; RTx/RTX: rituximab; CYC: cyclophosphamide; AZA: azathioprine; RCT: randomized controlled trial; GFR: glomerular filtration rate; IV: intravenous; BVAS: Birmingham Vasculitis Activity Score; PR3-ANCA: proteinase 3-ANCA; MPO-ANCA: myeloperoxidase-ANCA; RR: relative risk. Here, MPO is linked to granulomatosis with polyangiitis.