In contrast to studies [8, 9, 13] related to the RAVE trial, which have indicated that GPA with positive proteinase-3 (PR3) is predominant in patients with AAV from the United States and The Netherlands, Japanese patients with AAV appear to have a higher incidence of MPA than of GPA, and they show a predominance of myeloperoxidase (MPO)-ANCA. The gene discussed is MPO; the disease is microscopic polyangiitis.