It has three main clinical types, granulomatous with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatous polyangiitis (EGPA) [2], in which serum markers include protease 3 (PR3) and myeloperoxidase (MPO) [3,4] that are released under the stimulation of pathogens [5–8]. Here, MPO is linked to microscopic polyangiitis.