title: Major histocompatibility complex class I and II detection as a diagnostic tool in idiopathic inflammatory myopathies.
abstract: BACKGROUND
  Muscle biopsy is at present the gold standard for the diagnosis of idiopathic inflammatory myopathies (IIMs), which include dermatomyositis, polymyositis, and inclusion body myositis. Currently, there is no definite diagnostic marker that helps in the discrimination of different subgroups of IIMs and the discrimination of IIMs from other clinical and morphologic mimics. Major histocompatibility complex (MHC) class I and II antigens are not expressed on normal muscle fibers.
  
  
  OBJECTIVE
  To determine the diagnostic utility of MHC class I and II antigen expression on the muscle biopsies from patients with various neuromuscular disorders and to validate its addition in the existing diagnostic armamentarium.
  
  
  METHODS
  Expression of MHC class I and II antigen was studied on 126 muscle biopsies, of which 62 were IIMs and 64 were controls (taken from patients with other neuromuscular disorders).
  
  
  RESULTS
  When compared with controls, the sensitivity of MHC class I expression for diagnosis of IIMs was 88.7% (100%, 81.6%, and 100% for dermatomyositis, polymyositis, and inclusion body myositis, respectively), with a specificity of 89.1%. The specificity of MHC class II expression was 100% for all IIMs.
  
  
  CONCLUSIONS
  Detection of MHC class I and II antigen expression is extremely helpful in the diagnosis of IIMs and has high sensitivity and specificity, especially in dermatomyositis. This expression can be used as a diagnostic tool in discriminating IIMs from other muscle diseases in which it is either absent or weakly expressed.
authors.affiliation: Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Ayushi
authors.initials: A
authors.lastname: Jain
authors.forename: Mehar Chand
authors.initials: MC
authors.lastname: Sharma
authors.forename: Chitra
authors.initials: C
authors.lastname: Sarkar
authors.forename: Rohit
authors.initials: R
authors.lastname: Bhatia
authors.forename: Sumit
authors.initials: S
authors.lastname: Singh
authors.forename: Rohini
authors.initials: R
authors.lastname: Handa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003882:Dermatomyositis / Q000175:diagnosis; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000032:analysis*; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000276:immunology*; D009220:Myositis / Q000175:diagnosis* / Q000276:immunology; D018979:Myositis, Inclusion Body / Q000175:diagnosis; D017285:Polymyositis / Q000175:diagnosis; D012189:Retrospective Studies
chemical_list: D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II