title: Anti-PM/Scl antibodies are found in Japanese patients with various systemic autoimmune conditions besides myositis and scleroderma.
abstract: BACKGROUND
  Anti-PM/Scl antibodies are associated with polymyositis (PM)/systemic scleroderma (SSc) overlap syndromes and are also found in other systemic autoimmune diseases. Although anti-PM/Scl reactivity is found in 3-11% of PM or SSc patients and in approximately 25% of PM/SSc overlap patients, previous large studies of Japanese patients with scleroderma reported that anti-PM/Scl are not found in Japanese patients at all. The PM/Scl autoantigen complex comprises 11-16 different polypeptides; ELISA with PM1-α peptide, which is a major epitope of the PM/Scl complex, has frequently been used for the detection of these antibodies in recent studies. However, no ELISA kit is commercially available in Japan.
  
  
  METHODS
  In this study, we developed an immunoassay for measuring antibodies against recombinant PM/Scl-100 and PM/Scl-75 polypeptides, which are the two major targets of the complex, and we investigated their presence in 600 Japanese patients with various systemic autoimmune conditions. Immunoprecipitation analysis using the recombinants in addition to traditional radiolabeled cell extracts were also applied to ELISA-positive sera.
  
  
  RESULTS
  In ELISA, 11 patients were positive for anti-PM/Scl-100 antibodies and 7 of these 11 patients were also positive for anti-PM/Scl-75 antibodies. Immunoprecipitation analysis using the recombinants in addition to traditional radiolabeled cell extracts confirmed that 9 out of these 11 patients immunoprecipitated the typical sets of PM/Scl proteins. In total, 4/16 (25%) undifferentiated connective tissue disease (UCTD) patients, 3/126 (2.4%) dermatomyositis patients, 1/223 (0.4%) SSc patients, 1/88 (1.1%) Sjögren's syndrome patients, 0/123 patients with systemic lupus erythematosus, 0/17 patients with overlap syndrome and 0/7 patients with PM were judged to be positive for anti-PM/Scl antibodies.
  
  
  CONCLUSIONS
  This is the first report of Japanese autoimmune patients with anti-PM/Scl antibodies. In Japanese patients, anti-PM/Scl antibodies are only very rarely found, and they are not always specific for dermatomyositis (DM) or SSc; they are also present in various autoimmune conditions with the highest prevalence being in UCTD. All anti-PM/Scl-positive DM cases are complicated with interstitial lung disease and/or cancer, while no life-threatening involvement was found in other anti-PM/Scl-positive cases. Further studies on larger cohorts are necessary to define the clinical significance of anti-PM/Scl antibodies in autoimmune diseases.
authors.affiliation: Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan. ymuro@med.nagoya-u.ac.jp.|Division of Connective Tissue Disease and Autoimmunity, Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan. ymuro@med.nagoya-u.ac.jp.
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Muro
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, 606-8507, Japan. hosono25@kuhp.kyoto-u.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hosono
authors.affiliation: Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan. kazusugi@med.nagoya-u.ac.jp.
authors.forename: Kazumitsu
authors.initials: K
authors.lastname: Sugiura
authors.affiliation: Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan. yogawaderm@med.nagoya-u.ac.jp.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ogawa
authors.affiliation: Department of Rheumatology and Clinical Immunology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, 606-8507, Japan. mimorit@kuhp.kyoto-u.ac.jp.
authors.forename: Tsuneyo
authors.initials: T
authors.lastname: Mimori
authors.affiliation: Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan. makiyama@med.nagoya-u.ac.jp.
authors.forename: Masashi
authors.initials: M
authors.lastname: Akiyama
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D017285:Polymyositis / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology; D012595:Scleroderma, Systemic / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D001323:Autoantibodies