Classification criteria EULAR / ACR 2017 (Reference Lundberg IE, 2017)

The criteria summarize scores based on the following parameters with or without muscle biopsy available

Calculator, please see here

Criteria:

• Age at symptom start between 18 and 40 years
  • without biopsy 1,3 points, with biopsy 1,5 points
• Age at symptom start between 40 years or older
  • without biopsy 2,1 points, with biopsy 2,2 points
• Unbiased symmetrical, usually progressive in upper arms
  • without biopsy 0,7 points, with biopsy 0,7 points
• Unbiased symmetrical, usually progressive in thighs
  • without biopsy 0,8 points, with biopsy 0,5 points
• Neck flexor muscles (flexing head) relatively weaker than neck extensors
  • without biopsy 1,9 points, with biopsy 1,6 points
• Thigh muscles relatively weaker than calves
  • without biopsy 0,9 points, with biopsy 1,2 points
• Heliotrophic rash (around eyes)
  • without biopsy 3,1 points, with biopsy 3,2 points
• Gottron's papels (over the fingerjoints, elbows or knees)
  • without biopsy 2,1 points, with biopsy 2,7 points
• Gottrons` sign
  • without biopsy 3,3 points, with biopsy 3,7 points
• Dysphagia or oesophageal dysmotility
  • without biopsy 0,7 points, with biopsy 0,6 points
• Anti-Jo-1 antibody
  • without biopsy 3,9 points, with biopsy 3,8 points
• Elevated Enzymes (Without Biopsy 1,3 Points, With Biopsy 1,4 Points)
  • CK (creatine kinase) or
  • LD (lactate dehydrogenase) or
  • AST / ALT
• Muscle biopsy with endomyal infiltrations of mononuclear cells surrounding, but not penetrating muscle fibers (muscle cells)
  
  • Biopsy positive 1,7
• Muscle biopsy with perimyseal and / or perivascular infiltration of mononuclear cells
  • Biopsy positive 1,2
• Muscle biopsy with perifascular atrophy
  
  • Biopsy positive 1,9
• Muscle biopsy with "Rimmed vacuoles"
  
  • Biopsy positive 3,1

"Definite myositis" (at least 90% definite) if total summed score is at least 7,5 without biopsy or at least 8,7 where biopsy is available

Diagnostic criteria for poly- and dermatomyositis (Bohan and Peter)*

• 1. Symmetrical proximal muscle weakness
• 2. Elevated muscle enzymes in serum (CK, aldolase, AST, ALAT, LD)
• 3. EMG with polyphase MUP, "sharp waves" and repetitive discharges
• 4. Muscle biopsy; Degeneration, regeneration, necrosis, phagocytosis and interstitial mononuclear infiltrates
• 5. Typical exanthema (for empeleks heliotropic exanthema, Gottron's characters / papules)

• In order to diagnose DM, criterion 5 must be present

• Possible PM / DM = 2 criteria
• Probably PM / DM = 3 criteria
• Definitive PM / DM = 4 criteria

* The criteria assume that other causes of myopathy are excluded.

Revised classification criteria for poly / dermatomyositis (Targoff et al.)

• 1. Symmetrical proximal muscle weakness
• 2. Elevated muscle enzymes
• 3. EMG with myopathic "MUP", positive "sharp waves", repetitive discharges.
• 4. Muscle biopsy; Degeneration, regeneration, necrosis, phagocytosis and interstitial mononuclear infiltrates
• 5. One of the myositis specific antibodies
• 6. Typical eczema

Positive MRI examination for inflammation may replace criterion 1 or 2. In order to diagnose DM, criterion 6 must be present.

• Possible PM / DM = 2 criteria
• Probably PM / DM = 3 criteria
• Definitive PM / DM = 4 criteria

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