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 Glutamine at codon 4558 of the RYR1 protein, p.(Arg4558Gln). The maximum allele frequency for this variant among the six major gnomAD populations is EAS: 0.0001, a frequency consistent with pathogenicity for MHS. This variant has been reported in individuals with a personal or family history of congenital myopathy. No functional studies were identified for this variant. This variant does not reside in a hotspot for pathogenic variants that contribute to MHS. A REVEL score >0.85 (0.957) supports a pathogenic status for this variant, PP3_Moderate. This variant has been classified as a Variant of Unknown Significance. Criteria implemented: PP3_Moderate.