What you carry at this position in your DNA and what research says about it.
Anesthesia Reaction Risk: 9/10 evidence, 6 publications.
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Sample genotype (not yours): G/G
Typical Anesthesia and Muscle Response
Normal ryanodine receptor function protects against anesthesia-induced malignant hyperthermia. Muscle contraction and structure are expected to be typical.
What this genotype means: Normal anesthesia tolerance; Typical muscle function.
Sample genotype (not yours): A/A
Extremely High Risk of Muscle Disease and Anesthesia Reaction
Double copies of the A allele are exceptionally rare and cause severe susceptibility to malignant hyperthermia and congenital myopathies.
What this genotype means: Severe malignant hyperthermia risk; Congenital myopathy risk.
Sample genotype (not yours): G/A
High Risk of Severe Anesthesia Reaction
Presence of a single A allele causes susceptibility to life-threatening malignant hyperthermia during anesthesia. It is also linked to congenital muscle disorders and exertional muscle breakdown.
What this genotype means: Malignant hyperthermia risk; Muscle weakness and pain risk.
Gene function and biological role
Gene Function: The RYR1 gene encodes the ryanodine receptor 1, a massive calcium channel protein essential for skeletal muscle contraction [1]. Located in the sarcoplasmic reticulum membrane of muscle cells, this channel regulates the release of calcium ions into the cytoplasm [2]. This rapid calcium release triggers muscle fibers to contract in response to nerve signals [1]. Genetic variations in this gene can disrupt calcium flow, leading to muscle weakness, structural abnormalities, or life-threatening hypermetabolic reactions [2]. Understanding RYR1 function is critical for identifying individuals susceptible to severe anesthesia-induced complications [3].
Variant Impact: A single nucleotide substitution designated as p.Arg4737Gln alters a single amino acid in the ryanodine receptor 1 protein, replacing arginine with glutamine at position 4737 [4]. This specific change occurs in a critical region of the calcium channel, impairing its normal inactivation mechanisms [2]. As a result, the channel can become leaky or hyper-responsive to certain triggers [2]. This molecular defect underlies susceptibility to malignant hyperthermia and several congenital muscle disorders [5]. The variant is extremely rare in the general population but has high clinical significance [3].
Key Insight: A single copy of this rare variant can make common, otherwise safe inhaled anesthetics life-threatening.
Location: RYR1. Chromosome 19 · 19q13.2 · 38.6 Mb
Estimated prevalence by population
No frequency data available
This variant is not present in the gnomAD database.
Showing effects for G/G genotype
Pharmacogenomics
Anesthesia Response
Malignant Hyperthermia. Evidence: 9/10. Source: PMID 30236257. Typical.
Rare Genetic Disorders
Muscular & Neuromuscular Disorders
Central Core Myopathy. Evidence: 9/10. Source: PMID 16163667. Typical.
King-Denborough Syndrome. Evidence: 9/10. Source: PMID 16163667. Typical.
Multicore Myopathy. Evidence: 9/10. Source: PMID 16163667. Typical.
Lifestyle, Fitness & Aging
Injury Risk & Recovery
Muscle Breakdown. Evidence: 9/10. Source: PMID 16163667. Typical.
Showing effects for A/A genotype
Malignant Hyperthermia. Evidence: 9/10. Source: PMID 30236257. High Risk.
Central Core Myopathy. Evidence: 9/10. Source: PMID 16163667. High Risk.
King-Denborough Syndrome. Evidence: 9/10. Source: PMID 16163667. High Risk.
Multicore Myopathy. Evidence: 9/10. Source: PMID 16163667. High Risk.
Muscle Breakdown. Evidence: 9/10. Source: PMID 16163667. High Risk.
Showing effects for G/A genotype
Malignant Hyperthermia. Evidence: 9/10. Source: PMID 30236257. Increased Risk.
Central Core Myopathy. Evidence: 9/10. Source: PMID 16163667. Increased Risk.
King-Denborough Syndrome. Evidence: 9/10. Source: PMID 16163667. Increased Risk.
Multicore Myopathy. Evidence: 9/10. Source: PMID 16163667. Carrier.
Muscle Breakdown. Evidence: 9/10. Source: PMID 16163667. Increased Risk.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Two copies of the common G allele ensure that the ryanodine receptor 1 protein functions normally [1]. There is no elevated risk of malignant hyperthermia when exposed to volatile anesthetics or muscle relaxants [2]. Muscle structure remains typical, with no genetic predisposition to central core disease or other congenital myopathies associated with this variant [3]. Physical exertion is unlikely to trigger abnormal muscle breakdown or severe cramping from this specific genetic locus [4]. Standard medical care and routine anesthesia protocols can be followed safely [2].
Normal anesthesia tolerance; Typical muscle function.
Sample genotype: AA (Homozygous)
Two copies of the rare A allele severely compromise the function of the ryanodine receptor 1 calcium channel [1]. Exposure to standard volatile anesthetics or depolarizing muscle relaxants is highly likely to trigger a life-threatening hypermetabolic crisis [2]. This genotype is also associated with recessive congenital myopathies, including multicore myopathy and fiber type disproportion, which manifest as significant muscle weakness and structural abnormalities [3]. Severe muscle breakdown, pain, and weakness are highly expected, especially under physical stress [4].
Severe malignant hyperthermia risk; Congenital myopathy risk.
Sample genotype: GA (Heterozygous)
One copy of the rare A allele alters the structure of the ryanodine receptor 1 calcium channel [1]. This alteration makes the channel prone to uncontrolled calcium release when exposed to inhaled anesthetics like sevoflurane or muscle relaxants like succinylcholine [2]. This uncontrolled release can trigger malignant hyperthermia, a medical emergency characterized by rapid muscle rigidity and high body temperature [3]. Additionally, this dominant variant is associated with central core disease and King-Denborough syndrome, which cause muscle weakness [4]. Physical exertion or heat may also trigger muscle pain and rhabdomyolysis in some carriers [5]. It is vital to inform healthcare providers and anesthesiologists of this genetic status before any surgical procedure [2].
Malignant hyperthermia risk; Muscle weakness and pain risk.
Variants with shared genetic architecture
rs112563513 · RYR1 Gene · Chr 19 · Anesthesia Reaction Risk
rs118192122 · RYR1 Gene · Chr 19 · Anesthesia Reaction Risk
rs118192161 · RYR1 Gene · Chr 19 · Anesthesia Reaction Risk
Mechanistic models for muscle diseases and disorders originating in the sarcoplasmic reticulum.
Genetic epidemiology of malignant hyperthermia in the UK.
Genetic variation in RYR1 and malignant hyperthermia phenotypes.
Content updated August 2026.
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