Background

Malignant hyperthermia (MH) susceptibility is a heritable musculoskeletal disorder that can present as a potentially fatal hypermetabolic response to triggering anesthesia agents. Genomic screening for variants in MH-associated genes RYR1 and CACNA1S provides an opportunity to prevent morbidity and mortality. There are limited outcomes data from disclosing variants in RYR1, the most common MH susceptibility gene, in unselected populations. The authors sought to identify the rate of MH features or fulminant episodes after triggering agent exposure in an unselected population undergoing genomic screening including actionable RYR1 variants.

Methods

The MyCode Community Health Initiative by Geisinger (USA) is an electronic health record–linked biobank that discloses pathogenic and likely pathogenic variants in clinically actionable genes to patient-participants. Available electronic anesthesia and ambulatory records for participants with actionable RYR1 results returned through December 2020 were evaluated for pertinent findings via double-coded chart reviews and reconciliation. Descriptive statistics for observed phenotypes were calculated.

Results

One hundred fifty-two participants had an actionable RYR1 variant disclosed during the study period. None had previous documented genetic testing for MH susceptibility; one had previous contracture testing diagnosing MH susceptibility. Sixty-eight participants (44.7%) had anesthesia records documenting triggering agent exposure during at least one procedure. None received dantrolene treatment or had documented muscle rigidity, myoglobinuria, hyperkalemia, elevated creatine kinase, severe myalgia, or tea-colored urine. Of 120 possibly MH-related findings (postoperative intensive care unit admissions, hyperthermia, arterial blood gas evaluation, hypercapnia, or tachycardia), 112 (93.3%) were deemed unlikely to be MH events; 8 (6.7%) had insufficient records to determine etiology.

Conclusions

Results demonstrate a low frequency of classic intraanesthetic hypermetabolic phenotypes in an unselected population with actionable RYR1 variants. Further research on the actionability of screening for MH susceptibility in unselected populations, including economic impact, predictors of MH episodes, and expanded clinical phenotypes, is necessary.

Editor’s Perspective
What We Already Know about This Topic
  • Malignant hyperthermia (MH) susceptibility is a heritable musculoskeletal disorder that can present as a potentially fatal hypermetabolic response to triggering anesthesia agents.

  • RYR1 and CACNA1S are actionable MH-associated genes, and pathogenic and likely pathogenic variants in RYR1 account for 50 to 70% of MH cases and positive contracture cases.

What This Article Tells Us That Is New
  • In an unselected population of 130,048 adults who had screening, 152 participants had an actionable RYR1 variant disclosed. Of these, 68 participants had been exposed to a triggering anesthetic during a total of 126 procedures.

  • None of these exposures resulted in a typical intraanesthetic hypermetabolic phenotype of MH.

  • The utility of population screening for MH susceptibility merits further study.

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