Unifying Concepts

Classification Criteria for Polymyositis and Dermatomyositis

Dermatomyositis is an idiopathic disorder that includes an inflammatory myopathy and characteristic skin manifestations; polymyositis includes the inflammatory myopathy without the cutaneous findings.

Classification of Dermatomyositis/Polymyositis

* Without muscle weakness (amyopathic dermatomyositis or dermatomyositis sine myositis)
* With muscle weakness

  • Adult
    1. Associated with cancer
    2. Not associated with cancer
  • Pediatric

* Adult
* Pediatric
* Inclusion-body myositis
* Overlap (myositis associated with a connective tissue disease)

Classification Criteria for Polymyositis and Dermatomyositis
1. Skin lesions

  • Heliotrope: red-purple edematous erythema on the upper palpebra
  • Gottron’s sign: red-purple keratotic, atrophic erythema or macules on the extensor surface of finger joints
  • Erythema on the extensor surface of extremity joints, slight raised red-purple erythema over elbows or knees

2. Proximal muscle weakness (upper or lower extremity and trunk)
3. Elevated serum creatine kinase or aldolase level
4. Muscle pain on grasping or spontaneous pain
5. Myogenic changes on electromyography (short-duration, polyphasic motor unit potentials with spontaneous fibrillation potentials)
6. Positive anti-Jo-1 antibody test (histidyl-tRNA synthetase)
7. Nondestructive arthritis or arthralgias
8. Systemic inflammatory signs (temperature: more than 37°C [98.6°F] at axilla, elevated serum C-reactive protein level or accelerated erythrocyte sedimentation rate of more than 20 mm per hour by Westergren)
9. Pathologic findings compatible with inflammatory myositis (inflammatory infiltration of skeletal evidence of active regeneration may be seen)

Patients presenting with at least one finding from item 1 and four findings from items 2 through 9 are said to have dermatomyositis (sensitivity, 94.1 percent and specificity of skin lesions against systemic lupus erythema and systemic sclerosis, 90.3 percent). Patients presenting with at least four findings from items 2 through 9 are said to have polymyositis (sensitivity, 98.9 percent and specificity of polymyositis and dermatomyositis against all control diseases combined, 95.2 percent).



  1. Koler RA, Montemarano A. Dermatomyositis. Am Fam Physician. 2001 Nov 1;64(9):1565-72. [Medline]
  2. Drake LA, Dinehart SM, Farmer ER, Goltz RW, Graham GF, Hordinsky MK, Lewis CW, Pariser DM, Skouge JW, Webster SB, Whitaker DC, Butler B, Lowery BJ, Sontheimer RD, Callen JP,Camisa C, Provost TT, Tuffanelli DL. Guidelines of care for dermatomyositis. American Academy of Dermatology. J Am Acad Dermatol. 1996 May;34(5 Pt 1):824-9. [Medline]
  3. Tanimoto K, Nakano K, Kano S, Mori S, Ueki H, Nishitani H, Sato T, Kiuchi T, Ohashi Y. Classification criteria for polymyositis and dermatomyositis. J Rheumatol. 1995 Apr;22(4):668-74. [Medline]

Created: Jun 23, 2010

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