Myopathies

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Anonymous
ID:
117343
Filename:
Myopathies
Updated:
2011-11-16 18:54:33
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Myopathies
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Myopathies
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  1. Duchenne's Muscular Dystrophy Clinical Features
    • X-linked recessive so boys only
    • normal at birth but symptoms at onset of walking, wheelchair by 12 years on average
    • calf pseudohypertrophy (firm, rubbery)
    • cardiac abnormalities
    • respiratory deterioration due to scoliosis
    • mild cognitive impairment
  2. Becker's Muscular Dystrophy Clinical Features
    • similar to Duchenne's but milder
    • symptom onset-- about 12 years old complain of muscle cramps, some not until 4th decade or later
    • cardiomyopathy common, cognition usually normal
  3. Dystrophin Deficiency Pathology/Pathophysiology
    degeneration and phagocytosis of single muscle fibers or groups of fibers

    dystrophin thought to stabilize the muscle membrane during contraction/relaxation

    • Duchenne's-- deletion in dystrophin gene
    • Becker's-- dystrophin present but structurally abnormal
  4. Dystrophin Deficiency Dx
    • increased creatine kinase
    • EMG
    • genetic testing
    • if dystrophin deletion not detected-- muscle biopsy
  5. Dystrophin Deficiency Tx
    • prednisone for Duchenne's, not used for Becker's
    • supportive care
    • gene therapy
  6. Limb girdle muscular dystrophies
    • various mutations in dystrophin associated proteins and other muscle proteins
    • specific mutation influences age of onset and pattern of muscle involvement
  7. Myotonic Dystrophy Clinical Features
    • autosomal dominant
    • weakness and atrophy (especially across face)
    • myotonia
    • multisystem abnormalities
  8. Myotonic Dystrophy Pathogenesis
    • elongated trinucleotide repeat (CUG)
    • abnormal RNA transcript binds to proteins involved in RNA-splicing (interferes with other genes)
  9. Myotonic Dystrophy Dx and Rx
    Dx- EMG, genetic testing

    Rx- primarily supportive, ion channel blocker if myotonia substantial enough
  10. Non-dystrophic hereditary myopathies
    • abnormal glycogen metabolism
    • phosphofructokinase deficiency
    • mitochondrial myopathies
    • channelopathies
  11. Dermatomyositis and Polymyositis Clinical Features
    • symmetric proximal muscle wasting and weakness
    • progresses gradually (weeks) for DM and (months) PM
    • DM-- characteristic rash on face and hands, children and young adults, malignancy in 10-20%
  12. Inclusion Body Myositis Clinical Features
    • prominent involvement forearm flexors and knee extensors
    • asymmetric issues, asymmetric dysphagia common
    • after age 50
  13. Inflammatory Myopathies Pathology
    • segmental muscle fiber necrosis
    • muscle fiber regeneration
    • mononuclear cell inflammation
    • IBM-- vacuolar inclusion containing beta amyloid, tau, and TDP-43 in muscle fibers
    • DM- perivascular inflammation, microinfart
    • PM- inflammatory cells among muscle fibers
  14. Inflammatory Myopathies Dx
    • increase CK
    • EMG
    • muscle bx for definitive Dx
  15. Inflammatory Myopathies Management
    • DM/PM prednisone
    • IBM none known

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