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Myopathies
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- 2. SLOs • Basics ofmuscle histology / ultrastructure • Inherited / Acquired • Characteristics • Clinical significance
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- 4. Normal pattern ofmuscle fibers Type 1 – aerobic / slow twitch Type 2 – anaerobic / fast twitch
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- 6. Neuropathic v/s Myopathic Groupedatrophy Patchy atrophy followed by inflammation and regeneration
- 7. Neuropathic v/s Myopathic Lossof checkerboard pattern Checkerboard pattern maintianed
- 8. Classification of Myopathies •Inherited – Dystrophinopathies – Myotonic dystrophy – Limb-girdle muscular – Emery-Dreifuss – Fascioscapulohumeral dystrophy – Channelopathies – Metabolic – Mitochondrial • Acquired – Inflammatory – Toxic
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- 10. Dystrophinopathies Duchene Becker Dystrophin genemutation Dystrophin gene mutation 1in 3500 live births Less common Always fatal Less severe -Largest human gene -2.4 mega bases -1% of X chromosome
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- 12. Dystrophinopathies • Pathogenesis – Dystrophin-glycoproteincomplex stabilizes the muscle cell – Involved in cell signaling – Defects make muscle cells vulnerable to membrane tears – Lead to calcium influx, and disrupt intracellular signaling – Results in myofiber degenerationents.
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- 14. Myotonic dystrophy • Autosomaldominant • Dystrophia myotonica protein kinase • CTG repeat – Anticipation
- 15. Limb-girdle muscular dystrophy •Autosomal • Heterogeneous
- 16. Emery-Dreifuss muscular dystrophy • Autosomal/ X linked • Structural proteins in nucleus • Emerin / Lamin • Cardiac involvement also known
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- 18. Ion channel myopathies •Familial • Relapsing episodes • Hypotonic paralysis • Genes encoding for ion channels • Hyperkalemic periodic paralysis • Malignant hyperthermia • Central core disease
- 19. Myopathies due toinborn errors of metabolism • Glycogen synthesis • Lipid handling • Storage disorders • Excerise / fasting induced muscle damage • Rhabdomyolysis
- 20. Mitochondrial Myopathies • Maternalinheritance pattern • Proximal muscle and external ophthalmoplegia
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- 22. Inflammatory myopathies • Primary –Polymyositis – Dermatomyositis – Inclusion body myositis • Secondary – SLE – Sarcoidosis
- 23. Polymyositis • Autoimmune disorder •MHC class I molecules • Endomysial inflammatory infiltrates containing CD8+ • Myofiber necrosis and subsequent regeneration
- 24. Dermatomyositis • Most common •Children – isolated entity • Adults - paraneoplastic • Autoimmune basis • Perivascular mononuclear cell infiltrates • Paraseptal or perifascicular pattern of myofiber necrosis • Autoantibodies specific
- 25. Inclusion body myositis •Most common > 60 years • Hallmark - rimmed vacuoles (tau, β-APP • is it degenrative ? • Myopathic changes, mononuclear cell infiltrates, endomysial fibrosis, and fatty replacement
- 26. Toxic myopathy • Thyrotoxicmyopathy – acute or chronic proximal muscle weakness – myofiber necrosis and regeneration • Ethanol myopathy – after binge drinking – rhabdomyolysis with acute muscle pain – Myocyte swelling, necrosis, and regeneration • Drug myopathy – Statins – myopathic injury, without an inflammatory component.
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