Phenotypic Evidence for the Reclassification of the RYR1 p.(Glu4410Asp) Variant: From Uncertain Significance to Likely Benign

Malignant Hyperthermia Susceptibility (MHS) is most commonly caused by pathogenic variants in the RYR1 gene. The proliferation of RYR1 Variants of Uncertain Significance (VUS) on diagnostic genetic panels poses a significant clinical challenge, often leading to unnecessarily complex clinical concerns. We report the case of a 27-year-old African American female with a personal history of recurrent exertional rhabdomyolysis found to have a heterozygous RYR1 c.13230G>C p.(Glu4410Asp) variant. She later tested negative via the gold-standard Caffein–Halothane Contracture Test (CHCT). A negative CHCT test with an in silico Rare Exome Variant Ensemble Learner (REVEL) score of 0.171 meets the ClinGen MHS Variant Curation Expert Panel (VCEP) criteria for reclassification of the variant to Likely Benign. Additionally, the high allele frequency isolated within the African American (AA) population suggests a benign, ancestry-specific polymorphism maintained within the AA population rather than a pathogenic MHS mutation. Therefore, reclassifying the variant to Likely Benign prevents unnecessary muscle biopsies and alterations to perioperative anesthetic management and reduces the need for family cascade testing, and reduces use of potentially suboptimal alternative anesthetic protocols.