Résumé :
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Myopathies which primarily affect the thick filament protein myosin may be hereditary or aquired. Hereditary myosin myopathies are a newly emerged group of diseases caused by mutations in skeletal muscle myosin heavy chain (MyHC) genes. The phenotypes of these diseases are varied, ranging from prenatal onset non-progressive arthrogrypotic syndromes to adult-onset progressive muscle weakness. Most of the mutations described in MYH7 (slow/?-cardiac MyHC) are associated with hypertrophic/dilated cardiomyopathy, with no skeletal muscle involvement. However, some mutations are associated with two distinct skeletal myopathies, namely Laing distal myopathy and myosin storage myopathy. A myopathy associated with a specific mutation in MYH2 (fast, IIa MyHC ) is associated with congenital joint contractures and external ophthalmoplegia. Mutations in MYH3 (embryonic MyHC) and MYH8 (perinatal MyHC) are associated with distal arthrogryposis syndromes with no or minor muscle weakness. The acute quadriplegic myopathy (AQM) represents an acquired disorder characterized by severe muscle weakness and atrophy of spinal nerve innervated limb and trunk muscles, associated with altered muscle membrane properties and a preferential loss of myosin and myosin-associated thick filament proteins. Prolonged mechanical ventilation, muscle unloading, postsynaptic block of neuromuscular transmission, sepsis and systemic corticosteroid hormone treatment have been forwarded as important triggering factors.
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