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 cysteine at codon 4861 of the RYR1 protein, p.(Arg4861Cys). This variant was not present in a large population database (gnomAD) at the time this variant was interpreted. This variant has been reported in an individual with a personal or family history of an MH episode and a positive in vitro contracture test (IVCT) or caffeine halothane contracture test (CHCT) result (if the proband was unavailable for testing, a positive diagnostic test result in a mutation-positive relative was counted), PS4_Supporting (PMID:30236257). This variant has also been reported in many individuals with myopathy without reported MH events, these individuals were not considered for PS4 as this assessment is specific to MH inherited in an autosomal dominant pattern (PMID:12565913, PMID:16621918, PMID:17226826 and others). Another variant has been assessed as likely pathogenic occurs at this codon, p.(Arg4861His), PM5_Supporting (PMID: 23558838). 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, PM1_Supporting (PMID: 21118704). A REVEL score >0.85 (0.912) supports a pathogenic status for this variant, PP3_Moderate. This variant has been classified as a Variant of Uncertain Significance. Criteria implemented: PS4_Supporting, PM1_Supporting, PM5_Supporting, PP3_Moderate.