RYR1 and myopathy: On the pathological level, central and multiple internalized nuclei are often the principal histopathological feature when muscle biopsy is performed early in life (Jungbluth et al., 2007), but other histopathological features typically associated with recessive RYR1-related myopathies – marked type 1 predominance or uniformity, fiber type disproportion and cores – may evolve over time (Bevilacqua et al., 2011).