MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by necrotizing vasculitis, predominantly affecting small vessels associated with myeloperoxidase (MPO)-ANCA or proteinase 3 (PR3)-ANCA according to the Chapel Hill Consensus Conference (CHCC2012) [1].