Vancouver IM LMR

Today’s noon report worked through the case of a 78 year old man with a history of pontine stroke, dyslipidemia, hypertension, and T2DM who presented with 3 weeks of progressive, symmetric proximal muscle weakness and a CK of 14 000. He was eventually diagnosed with statin-induced immune-mediated necrotizing myopathy!

See the didactic slide deck here.

Key take home points:

• Approach to weakness (broadly) and elevated CK

• Immune-mediated myopathies
  • Investigations and diagnosis
    • Clinical history and physical
    • Labs: CK, ANA, ENA, myositis autoantibodies, mitogen panel (CRP not always elevated!)
    • EMG, MRI, muscle biopsy
  • Clinical associations
    • Highly associated with malignancy – workup includes age-appropriate malignancy screen!
  • Major subtypes:
    • Classic dermatomyositis
      • Chronic-onset symmetric proximal weakness with classic cutaneous findings (Heliotrope rash, Gottron’s papules, shawl sign, nail changes etc)
      • Associated with ILD in 25% cases
    • Anti-synthetase antibody syndrome
      • Symmetric proximal weakness, ILD, mechanic’s hands, Raynaud’s phenomenon, arthritis, fever
      • Often anti-Jo-1 positive
    • Immune-mediated necrotizing myopathy
      • Rapidly progressive, symmetric proximal weakness with high CK
      • Often associated with HMGCR Ab+ which is often associated with statin use
      • You can develop statin-associated muscle adverse events at any time, even if you have been on the medication for years!
    • Inclusion body myositis
    • MDA5 dermatomyositis
      • Associated with rapidly progressive ILD (these patients often need lung transplant), classic cutaneous findings, but less muscle involvement