Malignant hyperthermia related DNA analysis (RYR1 gene) in Belgian families

This retrospective study sununarizes the results of DNA testing (Ryanodine receptor 1 (RYR1) gene sequencing) in a cohort of 34 Belgian families with proven Malignant Hyperthermia susceptibility. Eighteen different RYR1 sequence variants were found in 25 families. The most prevalent variant was p.Gly341Arg, detected in 7 families. Ten of the 18 variants are considered to be pathogenic, the remainder being 'variants of uncertain significance'. Complete phenotype and genotype concordance was obtained in 15 families ; in 7 discordance was found ; in 3 insufficient data did not allow to conclude. Discordance could be attributed to either limits in specificity of the in vitro contracture test, wrong blood sampling, or the possibility of more than one RYR1 variant in a particular family. Even though this study reflects the known important diverseness of RYR1 variants, genetic testing can secure a diagnosis of Malignant Hyperthennia susceptibility in almost 50% of the Belgian families with known Malignant Hyperthermia.