title: Genetic Myopathies Initially Diagnosed and Treated as Inflammatory Myopathy.
abstract: OBJECTIVE
  Differentiating genetic myopathies from inflammatory myopathies can be challenging because of multiple overlapping clinical features. Examples are presented to highlight important clinical features that assist in the differentiation between the two.
  
  
  METHODS
  Clinical features including age at onset, history, pattern of weakness, serum creatine kinase activity, electromyography findings, and muscle biopsies are reported in six patients initially thought to have an inflammatory myopathy in whom the final diagnosis was a genetic myopathy.
  
  
  RESULTS
  All six patients met Bohan and Peter criteria for at least probable idiopathic polymyositis and were subsequently found to have a genetic myopathy (4 DYSF, RYR1, and GNE). The key distinguishing clinical were minimal to no response to immunosuppression and atypical involvement of distal muscles in the majority of cases.
  
  
  CONCLUSIONS
  Patients diagnosed with inflammatory myopathies should be reevaluated for the possibility of a genetic myopathy if they fail to respond to a course of disease-modifying agents and/or there is atypical distal muscle involvement.
authors.affiliation: 1McMaster University,Department of Pediatrics,Hamilton,Ontario,Canada.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Tarnopolsky
authors.affiliation: 1McMaster University,Department of Pediatrics,Hamilton,Ontario,Canada.
authors.forename: Erin
authors.initials: E
authors.lastname: Hatcher
authors.affiliation: 2St. Michaels Hospital,University of Toronto,Toronto,Ontario.
authors.forename: Rachel
authors.initials: R
authors.lastname: Shupak
mesh_terms: D000293:Adolescent; D000328:Adult; D003402:Creatine Kinase / Q000097:blood; D000073939:Dysferlin; D004576:Electromyography; D005260:Female; D005820:Genetic Testing; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D009097:Multienzyme Complexes / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics; D009132:Muscles / Q000473:pathology; D009154:Mutation / Q000235:genetics; D009220:Myositis / Q000097:blood / Q000175:diagnosis / Q000235:genetics / Q000628:therapy; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics; D055815:Young Adult
chemical_list: C114839:DYSF protein, human; D000073939:Dysferlin; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; C482901:UDP-N-acetylglucosamine 2-epimerase - N-acetylmannosamine kinase; D003402:Creatine Kinase
keywords: dysferlinopathy; genetic myopathy; genetics; inflammatory diseases; inflammatory myopathy; myopathy; myositis