II. Pathophysiology

  1. Group I of Polymyositis disorders (accounts for 33%)

III. Epidemiology

  1. Incidence higher in women by ratio of 2:1

IV. Course

  1. Insidiously progressive over weeks to years

V. Symptoms: Proximal limb weakness

  1. Hip and Thigh weakness (Most significant)
    1. Difficult rising from seated/kneeling position
    2. Difficult climbing/descending stairs
    3. Unable to walk (5%)
  2. Shoulder Muscle Weakness
    1. Difficulty reaching overhead (e.g. combing hair)
  3. Buttock, thigh, or calf aching (10%)
    1. Tenderness to palpation (20%)

VI. Symptoms: Other

  1. Dysphagia (25%)
  2. Weakness of extensor neck muscles
  3. Respiratory Impairment (5%)
  4. Cardiac involvement (30%)
    1. Electrocardiogram (EKG) change or arrhythmia
    2. Congestive Heart Failure secondary to Myocarditis

VII. Signs

  1. Proximal Muscle Weakness
  2. Distal muscle sparing in 75%
  3. Muscles tender to palpation with signs of atrophy
  4. Gait slow and waddling

VIII. Differential Diagnosis

IX. Evaluation

X. Management

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