STAC3 and congenital myopathy with cores: Congenital myopathies arising due to pathogenic variants in genes encoding components of the triads or proteins involved in triad formation and maintenance, including RYR1 and STAC3, share many clinical features.26 27 These include hypotonia and axial weakness, which often tends to be static or slowly progressive, facial and bulbar weakness, resulting in dysphagia and dysarthria, ocular weakness, including ptosis and ophthalmoplegia and respiratory insufficiency.