RYR1 and myopathy: In addition to compound heterozygosity for recessive RYR1 mutations in one case, heterozygous RYR1 mutations inherited from an asymptomatic father and expressed on a haploinsufficient background were identified in three families; this has now been attributed to epigenetic allele silencing of the RYR1 gene as a novel mechanism in the pathogenesis of core myopathies [43].