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Inflammatory Myopathies

Inflammatory Myopathies. Katie DePlatchett, M.D. AM Report May 26, 2010. Infammatory Myopathies. Polymyositis Dermatomyositis Inclusion body myositis Overlap myositis – related to connective tissue disorder Cancer-associated myositis

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Inflammatory Myopathies

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  1. Inflammatory Myopathies Katie DePlatchett, M.D. AM Report May 26, 2010

  2. Infammatory Myopathies • Polymyositis • Dermatomyositis • Inclusion body myositis • Overlap myositis – related to connective tissue disorder • Cancer-associated myositis • myositis with clinical paraneoplastic features and without an overlap autoantibody

  3. Polymyositis • Symmetric proximal muscle weakness • Elevated serum muscle enzymes* • CK, CK-MB, AST, ALT, LD, Aldolase • Myopathic changes on EMG • Muscle biopsy • cellular infiltrate is predominantly within the fascicle with inflammatory cells invading individual muscle fibers • cell–mediated, increased numbers of cytotoxic CD8+ T cells, which appear to recognize an antigen on the muscle fiber surface

  4. Polymyositis - histopathology

  5. Dermatomyositis • Symmetric proximal muscle weakness • Elevated serum muscle enzymes • Myopathic changes on EMG • Muscle biopsy • humorally–mediated disorder (CD4 cells), cellular infiltrate, located principally in perifascicular regions, focused around blood vessels  • Rash

  6. Dermatomyositis - histology

  7. Dermatomyositis – skin findings • Gottron’s sign • Heliotrope rash • Shaw sign & V sign • Mechanic’s hands • Psoriasiform changes in scalp

  8. What about auto-antibodies??? • ANA present in up to 80% of • myositis-specific autoantibodies: • anti-Jo-1, highly specific, associated w/ ILD • anti-SRP antibodies • antibodies to Mi-2, (a nuclear helicase) • Not diagnostic but affects prognosis

  9. Inclusion body myositis • insidious onset • more prominent distal muscle weakness & atrophy (wrists, fingers, anterior tibial) • Asymmetric muscle involvement • On average, serum muscle enzyme levels are lower in IBM than in PM • presence of typical inclusion bodies on muscle biopsy

  10. Overlap Myositis • Myopathy associated with the other connective tissue diseases • scleroderma, systemic lupus erythematosus, mixed connective tissue disease • varies from clinically insignificant to typically severe PM or DM in which myopathy dominates the clinical picture • anti-Ro, anti-La, anti-Sm, or anti-ribonucleoprotein (RNP) antibodies.

  11. Differential Diagnosis • Drug induced: statins, colchicine, hydroxychloroquine, steroids, etoh, cocaine • HIV • ALS • Myasthenia gravis  • Muscular dystrophies • Inherited metabolic myopathies • Amyloid & Sarcoid myopathies

  12. Work-up • Serology: CK, CK-MB, AST, ALT, adolase, ANA, anti-Jo1, anti-SRP, anti-Sm, anti-Ro • Utox, HIV • Muscle biopsy • +/- EMGs • Age appropriate cancer screening for those with dermatomyositis

  13. Treatment • Steroids, PT/rehab • Minimal data of long-term follow-up of pts • PM: 50% were refractory to steroids • DM, 87% responded to steroids but 92% flared when therapy was tapered. • Overlap myositis: 89 to 100% responded to steroids, depended on specific antibodies. • Methotrexate or Azathioprine

  14. Prognosis • Determinants of prognosis: • the specific type of myositis • disease severity • delay in diagnosis • Certain autoantibody profile • PM: least likely to respond to steroids • Overlap myositis: most likely to respond to steroids.

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