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Necrotising autoimmune myopathy (NAM): antibodies seem to be specific markers in aiding diagnosis
  1. Marinos C Dalakas1,2
  1. 1Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
  2. 2Neuroimmunology Unit, University of Athens Medical School, Athens, Greece
  1. Correspondence to Professor Marinos C Dalakas, Department of Neurology, Thomas Jefferson University, Philadelphia, PA 19107, USA; mdalakas{at}

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Watanabe et al1 report on prospectively studied patients with necrotising autoimmune myopathy (NAM), diagnosed among 460 individuals with inflammatory myopathies (IM), over a 4-year period. This is the largest ever NAM cohort diagnosed with histological criteria and exclusion of genetically-defined muscular dystrophies. Among 387 patients (after excluding 16% with IBM), 30% had NAM with antibodies either against SRP (18%) or HMGCR (12%); another 13% had overlap myositis (OM), also a necrotising but perifascicular myositis, with anti-Jo-1 antibodies. Considering that antibodies are presently detected in 60–80% of NAM cases,2 this carefully studied population suggests that NAM is probably one of the commonest IM accounting, along with OM, for >50% of …

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  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

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