title: The co-existence of myasthenia gravis in patients with myositis: a case series.
abstract: OBJECTIVE
  Myositis and myasthenia gravis (MG) are both autoimmune disorders presenting with muscle weakness. Rarely, they occur simultaneously in the same patient. Since the management of myasthenia gravis differs from that of myositis, it is important to recognize when patients have both diseases. We reviewed the cases of 6 patients with both myositis and MG to identify clinical features that suggest the possibility of co-existing MG in myositis patients.
  
  
  METHODS
  We identified 6 patients with dermatomyositis or polymyositis and MG. We reviewed their medical records to assess their clinical presentations, laboratory findings, and electrophysiological features.
  
  
  RESULTS
  All 6 patients had definite dermatomyositis or polymyositis by the criteria of Bohan and Peter as well as electrophysiologic and/or serologic confirmation of MG. Among overlap patients, 5/6 (83%) had bulbar weakness, 2/6 (33%) had ptosis, and 1/6 (17%) had diplopia. Fatigable weakness was noted by 5/6 (83%) patients. Treatment with pyridostigmine improved symptoms in 5/6 (83%) patients. High-dose steroids were associated with worsening weakness in 2/6 (33%) patients.
  
  
  CONCLUSIONS
  Prominent bulbar symptoms, ptosis, diplopia, and fatigable weakness should suggest the possibility of MG in patients with myositis. A suspicion of MG may be confirmed through appropriate electrophysiologic and laboratory testing. In those with myositis-MG overlap, high-dose steroids may exacerbate symptoms and pyridostigmine may play an important therapeutic role.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD.
authors.forename: Julie J
authors.initials: JJ
authors.lastname: Paik
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Corse
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD. Electronic address: amammen@jhmi.edu.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Mammen
mesh_terms: D000328:Adult; D000368:Aged; D003882:Dermatomyositis / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications*; D017285:Polymyositis / Q000150:complications; D055815:Young Adult
keywords: Dermatomyositis; Myasthenia gravis; Myositis; Polymyositis