Criteria for myositis diagnosis and classification 4.5/5 (2)

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

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

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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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