RYR1 and congenital myopathy with cores: First, histopathology of muscle biopsies from patients harboring RYR1-related congenital myopathies show fiber type I predominance (Lawal et al., 2020; Jungbluth et al., 2005; Kondo et al., 2012; Bevilacqua et al., 2011; Lawal et al., 2018).