[MIM 255 310, 300 580]

Very rare.

It can be caused by a mutation of different genes:

-        TPM3 (1q21.3) (25-50 %) coding for the tropomyosin 3; autosomal dominant or recessive transmission

-        RYR1 (19q13.2) (20 %) coding for the recptor of the ryanodine; autosomal recessive transmission

-        ACTA1 (1q42.13) coding for the actin α1; autosomal dominant or recessive transmission

-        SELENON (1p36.11) coding for the selenoprotein N; autosomal dominant or recessive transmission

-        MYH7 (14q11.2) coding for the heavy chain 7 of the myosin; autosomal dominant transmission

-        MYL2 (12q24.11); autosomal recessive transmission

-        ZAK (2q31.1); autosomal recessive transmission

Histological examination: muscle fibers are unequal in size: the diameter of the type 1 fibers is smaller than those of type 2 by 30-40 %.

Generalized muscle weakness from the neonatal period or of more late-onset . Often causes moderate to severe respiratory insufficiency with facial or bulbar involvement or ophthalmoplegia. Scoliosis and muscle retractions appear quite rapidly.

Anesthetic implications:

to be considered as at risk for malignant hyperthermia

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. 
• 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