Please confirm topic selection

Are you sure you want to trigger topic in your Anconeus AI algorithm?

Updated: Mar 3 2022

Dermatomyositis / Polymyositis

Images papules.jpg
  • Snapshot
    • A 49-year-old woman with polymyositis presents to her physician’s office for weakness. She reports that she feels unusually tired and weak. She works as a makeup artist and in the past few weeks has experienced difficulty applying makeup on her clients. She finds it difficult to work while she has her arms raised. She denies any fevers, weight gain or loss, or any other motor deficits. Physical exam reveals decreased strength in her shoulders. No rash is appreciated. Laboratory evaluation reveals increased creatinine phosphokinase, positive antinuclear antibody, and positive anti-signal recognition particle. She is started on high-dose corticosteroids. (Polymyositis)
  • Introduction
    • Clinical definition
      • dermatomyositis is an autoimmune myopathy characterized by
        • symmetric proximal muscle weakness and rash
          • the clinical variant includes amyopathic dermatomyositis (dermatomyositis without myositis)
      • polymyositis is an autoimmune myopathy characterized by
        • symmetric proximal muscle weakness and no rash
  • Epidemiology
    • Demographics
      • female > male
      • typically in adults 30-50 years of age
      • if in children, considered juvenile dermatomyositis
    • Risk factors
      • drugs
      • physical exertion
    • Pathogenesis
      • dermatomyositis
        • an antibody-driven autoimmune disease characterized by perimysial inflammation and atrophy, resulting in muscle tissue damage
          • perimysium is closer to the skin and therefore has cutaneous manifestations – “dermato”
        • associated with CD4+ lymphocytes and complement activation
      • polymyositis
        • T-cell driven autoimmune disease characterized by endomysial inflammation
          • endomysium is farther from the skin and therefore has no cutaneous manifestations
        • associated with CD8+ lymphocytes
    • Associated conditions
      • interstitial lung disease
      • malignancy including
        • breast or ovarian cancer
        • prostate cancer
        • lung cancer
      • other connective tissue diseases
  • Presentation
    • Symptoms
      • progressive weakness in hips and shoulders
      • dysphagia
      • dysphonia
        • laryngeal muscle weakness
    • Physical exam
      • dermatomyositis
        • characteristic cutaneous findings
          • a photosensitive pink rash of the neck and trunk
            • shawl or V-sign, as it often appears as sunburn with V-neck t-shirt
          • purple/lilac or red rash around eyes and on eyelids (heliotrope rash)
            • can resemble a malar rash
          • raised violaceous, slightly scaly plaques, on bony prominences of the hands and elbows (Gottron papules)
            • “mechanic’s hands”
      • polymyositis and dermatomyositis
        • proximal muscle weakness in the shoulders and hips
          • difficulty combing hair
          • difficulty raising arms
          • difficulty rising from a chair
  • Studies
    • Labs
      • ↑ creatinine phosphokinase (CPK or CK)
      • ↑ creatine kinase-MB (CK-MB)
      • ↑ aldolase
      • ↑ lactate dehydrogenase (LDH)
      • autoantibodies
        • + antinuclear antibody (ANA)
        • + anti-Jo-1 (~20% of patients)
        • + anti-signal recognition particle (SRP) (~5% of patients)
          • usually associated with polymyositis
        • + anti-Mi-2 (<10% of adults)
          • usually associated with dermatomyositis
    • Muscle biopsy
      • indication
        • diagnostic gold standard to differentiate between inflammatory and non-inflammatory myopathies 
      • findings
        • degenerating muscle fibers and inflammatory infiltrates
        • dermatomyositis
          • perimysial inflammation
        • polymyositis
          • endomysial inflammation
    • Making the diagnosis
      • based on clinical presentation and laboratory studies
  • Differential
    • Systemic lupus erythematosus
    • Localized scleroderma
    • Infectious myopathy
    • Myasthenia gravis
    • Inclusion body myositis
      • presents with weakness and elevated CRP/CK
      • biopsy demonstrates endomysial inflammation with basophilic-rimmed vacuoles
  • Treatment
    • Management approach
      • both diseases are often treated initially with a course of steroids, followed by long-term immunosuppression
    • Conservative
      • sun protection
        • indication
          • for all patients with dermatomyositis
    • Medical
      • systemic steroids (high-dose)
        • indications
          • for all patients with myositis as first-line therapy
          • 2-4 weeks with subsequent taper
      • antimalarial
        • indications
          • for patients with primarily skin manifestations of dermatomyositis
          • drugs
            • hydroxychloroquine
      • non-steroidal immunosuppression
        • indications
          • for refractory disease
          • for prevention of recurrence after steroid taper
          • drugs
            • methotrexate
            • azathioprine
  • Complications
    • Cardiomyopathy
    • Macrophage activation syndrome
  • Prognosis
    • Dermatomyositis
      • ↑ risk of malignancy (typically develops within 5 years of diagnosis)
1 of 0
1 of 8
Private Note

Attach Treatment Poll
Treatment poll is required to gain more useful feedback from members.
Please enter Question Text
Please enter at least 2 unique options
Please enter at least 2 unique options
Please enter at least 2 unique options