Polymyositis and Dermatomyositis

Polymyositis vs. Dermatomyositis

Polymyositis

Chronic inflammatory disease causing muscle weakness affecting proximal muscles (shoulders, hips, thighs). Onset in adults, but more common in women. No skin involvement.

Common Symptoms:

  • Progressive muscle weakness
  • Fatigue
  • Low-grade fever
  • Weight loss

Dermatomyositis

Similar to polymyositis but with skin involvement seen in both adults and children. The cause is Autoimmune (humeral and cellular) with increased cancer risk in adults.

Common Symptoms:

  • Muscle weakness
  • Rash: Heliotrope rash, Gottron’s papules, shawl sign, V-sign

Shared Features

  • Inflammatory myopathies
  • Diagnosed with muscle enzymes (CK), EMG, biopsy, and autoantibodies
  • Treatments: Corticosteroids, immunosuppressants, IVIG
  • Physical therapy is important
  • Routine cancer screening advised in dermatomyositis