[MIM 255 160, 608 358]

(myosinopathy)

Very rare. Autosomal dominant transmission (form A) [MIM 608 358] or recessive (form B) [MIM 255 160] of a mutation of the MYH7 gene (14q11.2) coding for the heavy chain 7 of the myosin of the type 1 fibers of the skeletal and cardiac muscles.

The clinical presentation varies widely:

-        muscle weakness that appears in infancy (A) or between 45 and 40 years of age (B), especially at the scapulohumeral level

-        moderately elevated CPK levels

-        hypertrophic cardiomyopathy and cardiac rhythm disorders

-        progressive respiratory insufficiency.

At the histological examination, hyalin bodies (composed of myosin) can be observed under the sarcolemma of the type1 muscle fibers.

Anesthetic implications:

echocardiography;  restrictive syndrome; contractures; a case of delayed onset of an echoguided block of the sciatic nerve has been described (secondary involvement of the Na voltage-dependent channels ?). To be considered at risk of rhabdomyolysis.

References : 

• Christiaens F, Van den Bergh PYK. 
  Les myopathies congénitales. 
  Louvain Med 2014 ; 133 : 478-90.
• North K, Wang C, Clarke N, Jungbluth H, Vainzof M, Dowling J et al. 
  Approach to the diagnosis of congenital myopathies. 
  Neuromuscul Disord 2014 ; 24 : 97-116. 
• Moosajee V, Egeler C, Walyers RJ, Topliss C, Ford S. 
  Delayed onset peripheral nerve blockade in a patient with congenital myopathy.
  Anaesthesia Cases 2014; 2: 50-4.
• Benarroch L, Bonne G, Rivier F, Hamroun D.
  The 2020 version of the gene table of neuromuscular disorders. Neuromusc Dis 2019 ; 29 : 980-1018 ou  http://www.musclegenetable.fr.

Updated: June 2021