Reasoning
The RYR1 VCEP PS4 Strong rule requires either at least 7 MH case points with popmax <=0.00006, or, when popmax MAF is >0.00006, an odds ratio >=18.7 comparing MH case points with gnomAD allele count and popmax <0.0038. Brandt et al. report Gly-2434-Arg in 7 of 105 unrelated MHS individuals/families, supplying 7 MH case points. gnomAD v4.1 reports popmax FAF 0.00010959, so the alternate path applies: 0.00010959 > 0.00006, and 0.00010959 < 0.0038. Using 7 variant-positive cases and 98 variant-negative cases versus 156 variant alleles and 1,613,848 nonvariant alleles in gnomAD v4.1, I computed OR = (7 x 1,613,848)/(98 x 156) = 738.94, 95% CI 337.82-1,616.35; therefore 738.94 >= 18.7 and PS4 Strong is met. The exact p.Gly2434Arg is independently reported in additional MHS cohorts and affected families, including 4/73 North American MHS individuals, 2/48 Swiss MHS families, and affected families with rhabdomyolysis/exertional myalgia.
VCEP rule
The prevalence of the variant in affected individuals significantly increased compared with the prevalence in controls.
* ≥7 MH case points. Probands with a personal or family history of an MH event are awarded 0.5 points, probands with a personal or family history of a positive (MHS) IVCT/CHCT are awarded an additional 0.5 points. Probands with multiple variants in RYR1 classified as VUS, likely pathogenic or pathogenic are not considered. Popmax in gnomAD ≤0.00006.
* For variants with popmax MAF gnomAD >0.00006, an odds ratio of ≥18.7 when comparing MH case points to allele count in gnomAD can qualify. Popmax in gnomAD must be <0.0038.
Evidence considered
- ClinGen RYR1 VCEP PS4 Strong rule: at least 7 MH case points can qualify when popmax in gnomAD is <=0.00006; for popmax MAF >0.00006, OR >=18.7 can qualify when popmax is <0.0038.
- Brandt et al. 1999, PMID:10484775, Results 'Screening for known mutations' and Table 1: Gly-2434-Arg was found in 7 of 105 unrelated MHS individuals/families; this supplies 7 MH case points.
- gnomAD v4.1, source record: popmax FAF = 0.00010959, variant allele count = 156, total allele number = 1,614,004; therefore 0.00010959 > 0.00006 and 0.00010959 < 0.0038.
- Case-control calculation performed from the reported counts: cases 7 variant-positive and 98 variant-negative individuals; gnomAD controls 156 variant alleles and 1,613,848 nonvariant alleles; OR = (7 x 1,613,848)/(98 x 156) = 738.94, 95% CI = 337.82-1,616.35; explicit comparison: 738.94 >= 18.7? yes.
- Sambuughin et al. 2001, PMID:11575529: Gly2434Arg occurred in 4 of 73 North American MHS individuals (5.5%), with positive CHCT responses and family cosegregation.
- Girard et al. 2001, PMID:11668625, Results/Table 2: G2434R occurred in 2 of 48 unrelated Swiss MHS families (4%).
- Jungbluth et al. 2013, PMID:23628358, Figure 1 caption/Results/Table 2: p.Gly2434Arg was identified in affected families with recurrent rhabdomyolysis and/or exertional myalgia.
Sources