title: Inflammatory myopathy with anti-signal recognition particle antibodies: case series of 100 patients.
abstract: BACKGROUND
  Anti-signal recognition particle (SRP) antibodies are used as serological markers of necrotizing myopathy, which is characterized by many necrotic and regenerative muscle fibers without or with minimal inflammatory cell infiltration. The clinical spectrum associated with anti-SRP antibodies seems to be broad.
  
  
  OBJECTIVE
  To describe the clinical characteristics, autoantibodies status, and neurological outcome associated with anti-SRP antibody.
  
  
  METHODS
  We studied clinical and laboratory findings of 100 patients with inflammatory myopathy and anti-SRP antibodies. Anti-SRP antibodies in serum were detected by the presence of 7S RNA using RNA immunoprecipitation. In addition, enzyme-linked immunosorbent assays (ELISAs) using a 54-kD protein of SRP (SRP54) and 3-hydroxyl-3-methylglutatyl-coenzyme A reductase (HMGCR) were also conducted.
  
  
  RESULTS
  The mean onset age of the 61 female and 39 male patients was 51 years (range 4-82 years); duration ≥ 12 months before diagnosis was seen in 23 cases. All patients presented limbs weakness; 63 had severe weakness, 70 neck weakness, 41 dysphagia, and 66 muscle atrophy. Extramuscular symptoms and associated disorders were infrequent. Creatine kinase levels were mostly more than 1000 IU/L. Histological diagnosis showed 84 patients had necrotizing myopathy, and apparent cell infiltration was observed in 16 patients. Anti-SRP54 antibodies were undetectable in 18 serum samples with autoantibodies to 7S RNA. Anti-HMGCR antibodies were positive in 3 patients without the statin treatment, however, were negative in 5 patients with statin-exposure at disease onset. All but 3 patients were treated by corticosteroids and 62 (77 %) of these 81 patients required additional immunotherapy. After 2-years treatment, 22 (27 %) of these 81 patients had poor neurological outcomes with modified Rankin scale scores of 3-5. Multivariate analysis revealed that pediatric disease onset was associated with the poor outcomes.
  
  
  CONCLUSIONS
  Anti-SRP antibodies are associated with different clinical courses and histological presentations.
authors.affiliation: Department of Neurology, Keio University School of Medicine, Tokyo, Japan. sgsuzuki@z3.keio.jp.
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Department of Neuromuscular Research, National Institute of Neuroscience, and Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry, Tokyo, Japan. nishikawa@ncnp.go.jp.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Nishikawa
authors.affiliation: Department of Allergy and Rheumatology, Nippon Medical School Graduate School of Medicine, Tokyo, Japan. kuwanam@nms.ac.jp.
authors.forename: Masataka
authors.initials: M
authors.lastname: Kuwana
authors.affiliation: Department of Neuromuscular Research, National Institute of Neuroscience, and Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry, Tokyo, Japan. nishimura@ncnp.go.jp.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nishimura
authors.affiliation: Department of Neurology, Keio University School of Medicine, Tokyo, Japan. yurica@z7.keio.jp.
authors.forename: Yurika
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Department of Neurology, Keio University School of Medicine, Tokyo, Japan. nakahara@a6.keio.jp.
authors.forename: Jin
authors.initials: J
authors.lastname: Nakahara
authors.affiliation: Department of Neurophysiology, Tokyo Medical University, Tokyo, Japan. yhayashi@tokyo-med.ac.jp.
authors.forename: Yukiko K
authors.initials: YK
authors.lastname: Hayashi
authors.affiliation: Department of Neurology, Keio University School of Medicine, Tokyo, Japan. nrsuzuki@a2.keio.jp.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Suzuki
authors.affiliation: Department of Neuromuscular Research, National Institute of Neuroscience, and Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry, Tokyo, Japan. nishino@ncnp.go.jp.
authors.forename: Ichizo
authors.initials: I
authors.lastname: Nishino
mesh_terms: D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D015415:Biomarkers; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009220:Myositis / Q000097:blood* / Q000175:diagnosis / Q000276:immunology*; D018271:Signal Recognition Particle / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D018271:Signal Recognition Particle