title: Japanese cases of neuromyelitis optica spectrum disorder associated with myasthenia gravis and a review of the literature.
abstract: BACKGROUND
  The incidence of concurrent myasthenia gravis (MG) and neuromyelitis optica spectrum disorder (NMOSD) is higher than what chance predicts, yet it remains unclear why MG and NMOSD appear concurrently.
  
  
  OBJECTIVE
  The purpose of the present study was to examine the clinical features of the concurrence of these diseases.
  
  
  METHODS
  Clinical details were analyzed retrospectively.
  
  
  RESULTS
  Three (0.5%) out of 631 MG patients had confirmed (n=2) or suspected (n=1) NMOSD. Two of these patients were women. All showed early-onset MG (EOMG) that preceded NMOSD and were positive for acetylcholine receptor antibody (AChR-Ab). Two patients were tested for aquaporin 4 antibody (AQP4-Ab) and were positive. Two patients were treated with a thymectomy that preceded NMOSD. Two patients had decreased frequency of regulatory T (Treg) cells. We identified in the literature 46 patients with both MG and NMOSD. Our results of female predominance, EOMG, MG preceding NMOSD, and positive AChR-Ab are consistent with previous descriptions.
  
  
  CONCLUSIONS
  This is the first report to examine the frequency of NMOSD in Japanese patients with MG. The reduction and/or dysfunction of Treg cells may be one cause of NMOSD development in MG.
authors.affiliation: Department of Neurology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan. Electronic address: riker1013@yahoo.co.jp.
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Ikeguchi
authors.affiliation: Department of Neurology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Department of Neurology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Medical Research Institute, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Neurology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kabasawa
authors.affiliation: Department of Neurology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
authors.forename: Shiori
authors.initials: S
authors.lastname: Hashimoto
authors.affiliation: Department of Neurology, Tokyo Medical University, Tokyo, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Masuda
authors.affiliation: Department of Neurology, Hanamaki General Hospital, Iwate, Japan.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Nagane
authors.affiliation: Department of Neurology, Hanamaki General Hospital, Iwate, Japan.
authors.forename: Kimiaki
authors.initials: K
authors.lastname: Utsugisawa
authors.affiliation: Department of Neurology, National Hospital Organization Sendai Medical Center, Sendai, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Neurology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Department of Neurology, Kamata General Hospital, Tokyo, Japan.
authors.forename: Hiroya
authors.initials: H
authors.lastname: Utsumi
authors.affiliation: Department of Neurology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Fujihara
authors.affiliation: Department of Neurology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Suzuki
authors.affiliation: Department of Neurology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Uchiyama
mesh_terms: D000328:Adult; D051401:Aquaporin 4 / Q000276:immunology; D044466:Asian People; D001323:Autoantibodies / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D009157:Myasthenia Gravis / Q000150:complications / Q000175:diagnosis / Q000276:immunology*; D009471:Neuromyelitis Optica / Q000150:complications / Q000175:diagnosis / Q000276:immunology*; D012189:Retrospective Studies; D013934:Thymectomy / Q000379:methods
chemical_list: D051401:Aquaporin 4; D001323:Autoantibodies
keywords: Acetylcholine receptor antibody; Myasthenia gravis; Neuromyelitis optica; Regulatory T cell; Thymectomy