Native Americans myopathy (NAM)

[MIM 255 995]

(Baily-Bloch myopathy, STAC3-related congenital myopathy)

Very rare. Congenital myopathy with autosomal recessive transmission of a mutation of STAC3 gene (12q13.3-14.1) coding for a protein involved in the excitation-contraction coupling in the striated muscle and interacting with the RYR1 and DHPR complexes. Frequent in the Lumbee American Indian population (North Carolina) but some cases have been recently reported in other populations.


It combines:

o        myopathy: the histology of which is aspecific (predominance of type I fibers) but with a major risk of malignant hyperthermia (29% of the cases) without any known associated mutation of the RYR1 gene; some cases have been reported as King syndrome

o        'myopathic' elongated, poorly expressive facies with a half-open mouth (tent-shaped), ptosis, short palpebral fissures; micrognathia and cleft palate are often present. Some cases are phenotypically close to Moebius or Carey-Fineman-Ziter syndromes (see those terms)

o        respiratory and nutritional problems in the neonate and infant: oral hypotonia, pulmonary inhalation

o        orthopedic abnormalities: arthrogryposis at birth, equinovarus foot, distal contractures, progressive scoliosis, short stature

o        normal intelligence but some delay in motor development associated with the myopathy.

o        normal CPK blood levels


Anesthetic implications:

risk of malignant hyperthermia; risk of difficult intubation


References : 



Updated June 2023