title: Classification and diagnostic investigation in inflammatory myopathies: a study of 99 patients.
abstract: OBJECTIVE
  Insights into the pathogenesis of inflammatory myopathies have led to new diagnostic methods. The aims of our study were (1) to evaluate the consequences of using the classification of Amato/European Neuromuscular Centre Workshop (ENMC) compared to that of Bohan and Peter; and (2) to evaluate any diagnostic benefit in using an extended pathological investigation.
  
  
  METHODS
  From a consecutive retrospective database, we evaluated 99 patients for classification. Patients with inclusion body myositis (IBM) were classified according to Griggs, et al. In addition to routine stainings and immunohistochemistry, a multilevel serial sectioning procedure was performed on paraffin-embedded material, to identify scarce pathological findings.
  
  
  RESULTS
  Classification according to Bohan and Peter could be performed for 83 of the 99 patients, whereas only 60 patients met the Amato/ENMC criteria, the latter resulting in the following diagnostic groups: IBM (n = 18), nonspecific myositis (n = 14), polymyositis (n = 12), dermatomyositis (n = 10), dermatomyositis sine dermatitis (n = 5), and immune-mediated necrotizing myopathy (n = 1). Most of the Amato/ENMC diagnostic groups harbored patients from several of the Bohan and Peter groups, which included a substantial group lacking proximal muscle weakness. The serial sectioning procedure was essential for classification of 9 patients (15%), and led to a more specific diagnosis for 13 patients (22%) according to Amato/ENMC.
  
  
  CONCLUSIONS
  The classification of Amato/ENMC was more restrictive, forming groups based on clinical criteria and specified myopathological findings, which clearly differed from the groups of the Bohan and Peter classification. An extended pathological investigation increased the diagnostic yield of a muscle biopsy and highlights the quantity and specificity of certain pathological findings.
authors: Department of Clinical and Experimental Medicine, Division of Neurology, Faculty of Health Sciences, Linköping University, Linköping, Sweden. olof.danielsson@lio.se
authors: Olof
authors: O
authors: Danielsson
authors: Björn
authors: B
authors: Lindvall
authors: Istvan
authors: I
authors: Gati
authors: Jan
authors: J
authors: Ernerudh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009220:Myositis / Q000145:classification* / Q000175:diagnosis / Q000473:pathology; D012189:Retrospective Studies
keywords: DERMATOMYOSITIS; IDIOPATHIC INFLAMMATORY MYOPATHIES; INCLUSION BODY MYOSITIS; INFLAMMATORY MYOPATHIES; POLYMYOSITIS