title: Clinico pathological study of adult dermatomyositis: Importance of muscle histology in the diagnosis.
abstract: OBJECTIVE
  To study the histological features on muscle biopsy and correlate them with clinical features, other laboratory data in adult patients to make a diagnosis of dermatomyositis (DM), applying the European Neuromuscular center (ENMC) criteria.
  
  
  METHODS
  Adult patients who fulfilled clinical, laboratory, and muscle biopsy findings according to ENMC criteria for DM during the period 2010-2013 were included in the study. Cryostat sections of muscle biopsy were reviewed with emphasis on Perifascicular atrophy (PFA), perivascular/endomysial inflammation. Muscular dystrophies and metabolic myopathies were excluded by appropriate immunohistochemistry and special stains.
  
  
  RESULTS
  The diagnosis of adult DM was made in 45 patients out of 170 clinically suspected idiopathic inflammatory myopathies. These included 33 definite, 4 probable, 7 possible sine dermatitis, and 1 amyopathic DM. All patients with definite DM had typical rash and proximal muscle weakness and muscle biopsy showed PFA with or without inflammation. Thirteen patients had quadriparesis, neck muscle weakness, dysphagia/dysphonia at presentation. Patients with probable DM had rash and showed perivascular/endomysial inflammation with no PFA. Possible DM sine dermatitis showed PFA with perivascular/endomysial infiltrates. One patient of amyopathic DM had typical heliotrope rash and characteristic skin biopsy.
  
  
  CONCLUSIONS
  Histological features are important for the diagnosis of DM. Relying on PFA for diagnosis of definite DM underestimates the true frequency of DM.
authors.affiliation: Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Sudhir Babu
authors.initials: SB
authors.lastname: Karri
authors.affiliation: Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Meena Anga Muthu
authors.initials: MA
authors.lastname: Kannan
authors.affiliation: Department of Rheumatology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Liza
authors.initials: L
authors.lastname: Rajashekhar
authors.affiliation: Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Megha S
authors.initials: MS
authors.lastname: Uppin
authors.affiliation: Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Sundaram
authors.initials: S
authors.lastname: Challa
keywords: Dermatomyositis; perifascicular atrophy; perivascular inflammation