title: Comparative investigation of respiratory tract involvement in granulomatosis with polyangiitis between PR3-ANCA positive and MPO-ANCA positive cases: a retrospective cohort study.
abstract: BACKGROUND
  The clinical characteristics of myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA) positive granulomatosis with polyangiitis (GPA) remain unclear, as does the difference between MPO-ANCA positive GPA and proteinase 3 (PR3)-ANCA positive GPA, especially with regard to the details of respiratory tract involvement. We investigated the differences in clinical, radiological, and histopathological features between PR3-ANCA positive GPA and MPO-ANCA positive GPA.
  
  
  METHODS
  We retrospectively reviewed 16 patients who were newly diagnosed with GPA between December 2000 and July 2014. One patient, who was positive for both PR3-ANCA and MPO-ANCA, was excluded. Our review was based on the European Medicine Agency (EMA) algorithm.
  
  
  RESULTS
  Fifty-six percent of GPA patients were positive for PR3-ANCA, 38 % for MPO-ANCA, and the remaining 6 % for both. The MPO-ANCA positive group included a greater number of females (67 %). There were no statistically significant differences in laboratory data, symptoms and signs, Birmingham Vasculitis Activity Score, or CT findings between the two groups. As for upper respiratory tract involvement, the most common manifestation was paranasal sinusitis, whereas lung nodules were most common as the lower respiratory tract involvement in both groups. Although the combination therapy with prednisone and cyclophosphamide was the most common initial treatment in both groups, the relapse rate in MPO-ANCA positive cases was lower than that of PR3-ANCA positive cases (17 % and 56 %, respectively).
  
  
  CONCLUSIONS
  A high prevalence of MPO-ANCA positive GPA was noted. No significant differences in clinico-radiological findings were observed except for the prevalence of relapse between the PR3-ANCA positive cases and MPO-ANCA positive cases, suggesting that the type of ANCA may be of little help in the diagnosis of GPA. Examination for granulomatous findings in the respiratory tract is important, even in MPO-ANCA positive cases. There is a need to accumulate more cases and conduct a further investigation in the future.
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. isatoshi0112@gmail.com.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ikeda
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. ma6390@kchnet.or.jp.
authors.forename: Machiko
authors.initials: M
authors.lastname: Arita
authors.affiliation: Department of Endocrinology and Rheumatology, Kurashiki Central Hospital, Kurashiki, Okayama, Japan. km13483@kchnet.or.jp.
authors.forename: Kenta
authors.initials: K
authors.lastname: Misaki
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. yumik1217@gmail.com.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kashiwagi
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. yi14402@kchnet.or.jp.
authors.forename: Yuhei
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Endocrinology and Rheumatology, Kurashiki Central Hospital, Kurashiki, Okayama, Japan. hy13574@kchnet.or.jp.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Yamada
authors.affiliation: Department of Pathology, Kurashiki Central Hospital, Kurashiki, Okayama, Japan. mh13029@hotmail.com.
authors.forename: Machiko
authors.initials: M
authors.lastname: Hotta
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. kabu568459@yahoo.co.jp.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Nishiyama
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. ai12306@kchnet.or.jp.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ito
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. mn13134@kchnet.or.jp.
authors.forename: Maki
authors.initials: M
authors.lastname: Noyama
authors.affiliation: Department of Radiology, Kurashiki Central Hospital, Kurashiki, Okayama, Japan. montpeti@kchnet.or.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Koyama
authors.affiliation: Department of Pathology, Kurashiki Central Hospital, Kurashiki, Okayama, Japan. notohara@kchnet.or.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Notohara
authors.affiliation: Department of Respiratory Medicine, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki, 710-8602, Japan. ishidat@kchnet.or.jp.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ishida
mesh_terms: D000368:Aged; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D005260:Female; D005500:Follow-Up Studies; D014890:Granulomatosis with Polyangiitis / Q000150:complications / Q000453:epidemiology / Q000276:immunology*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D017563:Lung Diseases, Interstitial / Q000453:epidemiology / Q000209:etiology / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D053146:Myeloblastin / Q000276:immunology*; D015995:Prevalence; D012189:Retrospective Studies
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D053146:Myeloblastin