Dermatomyositis

We discussed a young female with facial swelling, subacute onset generalized weakness without laboratory evidence of myositis (CK normal) and cutaneous findings of periorbital edema, heliotrope rash, gottron’s papules and mechanics hands diagnosed with amyopathic dermatomyositis with MDA-5+. Dermatomyositis is the autoimmune inflammation of perimysium and cutaneous findings; average age ~40 with female predominance. Cutaneous findings include heliotrope rash, periorbital and facial swelling, and violaceous erythema of face that INVOLVES nasolabial fold (unlike SLE). Patient may complain of difficulty combing hair, rising from a chair. Remember that in patients with DM, you should send the mymarker panel which surveys for many types of antibodies. Our patient was MDA-5+ which gives rise to ILD. Other antibodies include Anti-Mi2 which is seen in 30% of DM; ANA which is seen in 80% of DM; and finally antiJo-1 antibody which is seen in DM with Antisynthetase syndrome (ILD, Raynaud, arthritis, mechanics hands). Remember to survey for cancers (12x increased malignancy risk compared to age matched population). 

Myopathy ddx

  1. Autoimmune
    • Primary
      • Dermatomyositis
      • Polymyositis
      • Inclusion body myositis
    • Secondary
      • Vasculitis
  2. Non-inflammatory
    • Meds: Statin, Steroids
    • Toxins: EtOH
    • Critical Illness

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