title: Epidemiologic analysis of the clinical features of Japanese patients with polymyositis and dermatomyositis.
abstract: OBJECTIVE
  This study aimed to investigate the clinical characteristics of polymyositis/dermatomyositis (PM/DM) in Japan by analyzing data from the nationwide registration system.
  
  
  METHODS
  The data of the registration system in 2009 were analyzed to investigate patient numbers, sex, clinical symptoms, therapies, complications, and prognosis of PM/DM.
  
  
  RESULTS
  The total number of PM/DM cases was approximately 17,000, and the female/male sex ratio was 2.7:1. Almost all patients improved as a result of therapy, but many suffered from sequelae such as muscle weakness.
  
  
  CONCLUSIONS
  The results characterize significant aspects of Japanese PM/DM patients. However, a further prospective survey is required to clarify the true epidemiology and natural history of PM/DM.
authors.affiliation: a Department of Neurology , JA Toride Medical Center , Toride City , Ibaraki , Japan .
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tomimitsu
authors.affiliation: b Department of Public Health , Saitama Medical University Faculty of Medicine , Moroyama-Machi , Iruma-Gun , Saitama , Japan .
authors.forename: Akiko
authors.initials: A
authors.lastname: Ohta
authors.affiliation: b Department of Public Health , Saitama Medical University Faculty of Medicine , Moroyama-Machi , Iruma-Gun , Saitama , Japan .
authors.forename: Masaki
authors.initials: M
authors.lastname: Nagai
authors.affiliation: b Department of Public Health , Saitama Medical University Faculty of Medicine , Moroyama-Machi , Iruma-Gun , Saitama , Japan .
authors.forename: Motoko
authors.initials: M
authors.lastname: Nishina
authors.affiliation: c Department of Neurology and Neurological Science , Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University , Bunkyo-Ku , Tokyo , Japan , and.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ishihara
authors.affiliation: d Department of Medicine and Rheumatology , Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University , Bunkyo-Ku , Tokyo , Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kohsaka
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003882:Dermatomyositis / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000175:diagnosis* / Q000453:epidemiology; D017285:Polymyositis / Q000175:diagnosis* / Q000453:epidemiology; D015995:Prevalence; D011379:Prognosis; D012042:Registries; D063189:Symptom Assessment; D055815:Young Adult
keywords: Clinical features; Epidemiology; Nationwide registration system; Polymyositis and dermatomyositis (PM/DM)