Antineutrophil cytoplasmic antibody (ANCA) is well known to be pathogenic and to have diagnostic value for ANCA-associated vasculitis, and thus, myeloperoxidase-ANCA (MPO-ANCA) has been thought to be related to the pathogenesis of microscopic polyangiitis (MPA) [1]. Here, MPO is linked to anti-neutrophil cytoplasmic antibody-associated vasculitis.