This pathogenicity assessment is relevant only for malignant hyperthermia susceptibility (MHS) inherited in an autosomal dominant pattern. Variants in RYR1 can also cause other myopathies inherited in an autosomal dominant pattern or in an autosomal recessive pattern. Some of these disorders may predispose individuals to malignant hyperthermia. RYR1 variants may also contribute to a malignant hyperthermia reaction in combination with other genetic and non-genetic factors and the clinician needs to consider such factors in making management decisions. This sequence variant predicts a substitution of arginine with proline at codon 2452 of the RYR1 protein, p.(Arg2452Pro). This variant was not present in a large population database (gnomAD) at the time this variant was interpreted. This variant was reported in an individual who had a positive in vitro contracture test (IVCT) result, however, it was not clear that the individual had a personal or family history of an MH event and therefor PS4 was not implemented (PMID:19191333). No functional studies were identified for this variant. This variant resides in a region of RYR1 considered to be a hotspot for pathogenic variants that contribute to MHS, use PM1_Supporting to avoid overweighting with PM5 (PMID: 21118704). Another variant assessed as likely pathogenic occurs at this codon, p.(Arg2452Trp), PM5_Supporting (PMID:30236257). A REVEL score >0.85 (0.953) supports a pathogenic status for this variant, PP3_Moderate. This variant has been classified as a Variant of Uncertain Significance. Criteria implemented: PM1_Supporting, PM5_Supporting, PP3_Moderate.