Classifications of idiopathic inflammatory myositis

ClassificationType of myositisSubtypeRequired assessments#Description
Bohan and Peter's criteriaPMDefinite PM2Classical PM
Probable PM2
Possible PM2
DMDefinite DM2Classical DM
Probable DM2
Possible DM2
Overlap myositisCTM2Myositis with another CTD, irrespective of DM phenotype
CAMCAM2Myositis associated with cancer within 3 years
ENMC criteriaPMDefinite PM1Classical PM
Probable PM3
DMDefinite DM4Classical DM
Probable DM3
Amyopathic DM3DM rash, positive skin biopsy
Possible DM sine dermatitis3Typical biopsy without cutaneous involvement
Immune mediated necrotising myopathy3Necrotic muscle fibres, sparse inflammatory cells, MAC deposition on vessels at biopsy
Nonspecific myositis3No DM rash, nonspecific abnormalities at biopsy
Troyanov's criteriaPMPure PM5Myositis without extramuscular signs or antibodies
DMPure DM5DM as the first manifestation, rashes persist until diagnosis, high cutaneous score, DM-specific antibodies
Overlap myositis with DM features5Myositis as the first manifestation, low cutaneous score, no DM-specific antibodies
Adermatomyopathic DM5DM rash or calcinosis, positive skin biopsy
Clinically amyopathic DM5Amyopathic or hypomyopathic DM
Overlap myositisOverlap myositis5Myositis with at least one clinical overlap feature and/or an overlap autoantibody
CAMCAM5Clinical paraneoplastic features without an overlap autoantibody or anti-Mi-2
  • ENMC: European neuromuscular centre; PM: polymyositis; DM: dermatomyositis; CTM: myositis with other defined connective tissue disease; CTD: connective tissue disease; CAM: cancer associated myositis; MAC: membrane attack complex. #: the assessments are as follows. 1: physical examination, creatine phosphokinase and muscle biopsy; 2: assessments listed in 1 plus electromyography; 3: assessments listed in 2 plus muscular magnetic resonance imaging and autoantibodies; 4: physical examination and biopsy; 5: assessments listed in 2 plus autoantibodies.