The NM_000540.3:c.13013_13032del p.(Ala4338Glyfs*238) variant in RYR1 is a frameshift variant predicted to cause a premature stop codon in biologically-relevant-exon 91/106 leading to nonsense mediated decay in a gene in which loss-of-function is an established disease mechanism (PVS1). The highest population minor allele frequency in gnomAD v4.1 is 0.000004965 (5/1006982 alleles) in the European (non-Finnish) population, which is lower than the ClinGen Congenital Myopathies VCEP threshold (≤ 0.00000697) for PM2_Supporting, meeting this criterion (PM2_Supporting). This variant was found in trans with an RYR1 VUS NM_000540.3:c.1559T>C p.(Leu520Pro), in an adult woman affected with centronuclear myopathy which is highly compatible with recessive RYR1-related myopathy (PM3_Supporting, PP4, Internal VCEP contributors). In summary, this variant meets the criteria to be classified as pathogenic for autosomal recessive RYR1-related myopathy based on the ACMG/AMP criteria applied, as specified by the ClinGen Congenital Myopathies VCEP: PVS1, PM2_Supporting, PM3_Supporting, PP4 (Congenital Myopathies VCEP specifications Version 1: 8/7/2024)