Dermatomyositis – Morning Report 4/24/18

Definitions

– Polymyositis = muscle weakness without cutaneous signs
– Dermatomyositis = muscle weakness and cutaneous signs
– Amyopathic DM = cutaneous signs without muscle weakness

Epidemiology

  • F:M = 2:1
  • Peak incidence is age 40-50 but any age affected

Clinical Manifestations

  • Muscle weakness in 90% of PM patients and 50-60% in DM – in DM, rashes usually come before or at the same time
  • Symmetric and proximal muscle weakness
  • If +distal muscle weakness, usually mild
  • Insidious onset usually for months before they go to doctors
  • Skin findings
    • Usually on the joints involved whereas lupus shows cutaneous things between the joints
    • Gottron’s papules and heliotrope rash
    • Facial erythema – includes nasolabial folds
    • Shawl and v-signs
    • Holster sign – lateral aspect of the thigh
    • Inflammation of the nail fold
  • Lung disease – 10% of cases of DM and PM
  • Malignancy – generally parallels that of the general population distribution
  • Esophageal disease – weakness of the muscles à dysphagia/regurgitation
  • Cardiac disease – conduction abnormalities and arrhythmias, increased risk of MI

Labs

  • Elevated muscle enzymes (CK, LDH, AST, ALT, aldolase)
  • ANA + in 80% of patients and myositis ab in 30-40% of patients (Jo, Mi2, SRP)
  • Elevated serum and urine myoglobin
  • ESR is normal or midly elevated

EMG

  • Normal in 10% of the patients