What you carry at this position in your DNA and what research says about it.
Malignant Hyperthermia Risk: 9/10 evidence, 13 publications.
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Sample genotype (not yours): C/C
Typical Anesthesia Response
Normal RYR1 gene function with no elevated risk of malignant hyperthermia. Standard anesthetic protocols are generally safe.
What this genotype means: Normal response to standard volatile anesthetics; No inherited muscle weakness from this variant.
Sample genotype (not yours): C/T
High Malignant Hyperthermia Risk
Susceptibility to life-threatening reactions from specific general anesthetics. Alternative anesthesia options are typically recommended.
What this genotype means: Increased risk of severe reaction to volatile anesthetics; Potential risk of mild congenital muscle weakness.
Sample genotype (not yours): T/T
Extremely high risk of severe anesthesia reactions and congenital muscle disorders. Alternative anesthetic agents are essential.
What this genotype means: Extremely high risk of severe reaction to volatile anesthetics; High risk of congenital muscle weakness and developmental delay.
Gene function and biological role
Gene Function: The RYR1 gene encodes the skeletal muscle ryanodine receptor 1, which acts as a calcium release channel in the sarcoplasmic reticulum [1]. This channel plays a critical role in excitation-contraction coupling, releasing calcium ions to trigger muscle contraction [1]. Pathogenic variants in this gene can disrupt calcium regulation, leading to a life-threatening hypermetabolic state known as malignant hyperthermia [2]. Additionally, mutations in RYR1 are associated with congenital myopathies, including central core disease [3].
Variant Impact: The rs118192172 variant is a missense mutation in the RYR1 gene that changes the amino acid arginine to cysteine at position 614 [1]. This molecular alteration, often referred to as p.Arg614Cys, alters the functional properties of the calcium release channel [1]. It is a well-established risk factor that predisposes carriers to malignant hyperthermia during general anesthesia [3]. While highly associated with susceptibility, some individuals carrying this variant have undergone anesthesia without experiencing a crisis, indicating incomplete penetrance [4].
Key Insight: This variant is clinically silent under normal conditions, but exposure to common inhaled anesthetics can trigger a life-threatening muscle reaction.
Location: RYR1. Chromosome 19 · 19q13.2 · 38.5 Mb
Estimated prevalence by population
More than 99.9% of people in every population we have data for carry the CC genotype, so this position varies very little between people.
Global < 0.1%; European < 0.1%; African 0.0%; East Asian 0.0%; South Asian 0.0%; Americas 0.0%; Ashkenazi 0.0%; Middle Eastern 0.0%; Amish 0.0%.
Estimated CT genotype frequency.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Pharmacogenomics
Anesthesia Response
Malignant Hyperthermia. Evidence: 9/10. Source: PMID 1774074. Typical Risk.
Rare Genetic Disorders
Muscular & Neuromuscular Disorders
Central Core Myopathy. Evidence: 9/10. Source: PMID 11493496. Typical Risk.
King-Denborough Syndrome. Evidence: 9/10. Source: PMID 21795085. Typical Risk.
Congenital Myopathy. Evidence: 9/10. Source: PMID 21795085. Typical Risk.
Showing effects for C/T genotype
Malignant Hyperthermia. Evidence: 9/10. Source: PMID 1774074. High Risk.
Central Core Myopathy. Evidence: 9/10. Source: PMID 11493496. Increased Risk.
King-Denborough Syndrome. Evidence: 9/10. Source: PMID 21795085. Increased Risk.
Congenital Myopathy. Evidence: 9/10. Source: PMID 21795085. Healthy Carrier.
Showing effects for T/T genotype
Congenital Myopathy. Evidence: 9/10. Source: PMID 21795085. Increased Risk.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Normal function of the ryanodine receptor 1 channel is maintained by the common C allele [1]. There is no genetic predisposition to malignant hyperthermia or associated congenital myopathies from this specific locus [2]. Standard inhaled anesthetics and muscle relaxants do not pose an elevated risk of triggering a hypermetabolic crisis [3]. However, general medical history and other genetic factors still play a role in overall surgical safety. The ryanodine receptor is essential for regulating calcium flow in skeletal muscles. Without this specific mutation, the channel opens and closes normally during muscle contraction. This prevents the uncontrolled calcium leaks that characterize malignant hyperthermia. Standard surgical protocols remain appropriate unless other risk factors are present.
Normal response to standard volatile anesthetics; No inherited muscle weakness from this variant.
Sample genotype: CT (Heterozygous)
Presence of a single T allele is strongly associated with susceptibility to malignant hyperthermia [1]. Exposure to volatile anesthetics or succinylcholine can trigger uncontrolled calcium release, leading to muscle rigidity and dangerously high body temperature [2]. This variant is also linked to dominant congenital myopathies like central core disease, though clinical severity varies widely [3]. Some carriers may never experience symptoms, but taking precautions during surgery remains critical [4]. The underlying mechanism involves a leaky calcium channel in skeletal muscle cells. This leak can cause muscle cells to go into an intense, sustained metabolic state when exposed to triggers. Immediate treatment with specific rescue medications is required if a reaction occurs. Informing healthcare providers about this genetic status before any procedure is highly recommended.
Increased risk of severe reaction to volatile anesthetics; Potential risk of mild congenital muscle weakness.
Sample genotype: TT (Homozygous)
Inheriting two copies of the T allele is extremely rare and is associated with severe susceptibility to malignant hyperthermia [1]. It is also linked to recessive forms of congenital myopathies, such as multicore myopathy and fiber type disproportion [2]. Under standard volatile anesthesia, a life-threatening hypermetabolic crisis is highly likely to occur [3]. Alternative non-triggering anesthetics must be used to ensure safety during surgical procedures. The presence of two mutated alleles severely impacts the structure of the ryanodine receptor. This leads to profound calcium dysregulation in skeletal muscle tissue. Chronic muscle weakness and developmental delays are common clinical features of the associated myopathies. Specialized medical management is typically required to address both muscle health and anesthesia risks.
Extremely high risk of severe reaction to volatile anesthetics; High risk of congenital muscle weakness and developmental delay.
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
Genetic risk for malignant hyperthermia in non-anesthesia-induced myopathies.
A case of discordance between genotype and phenotype in a malignant hyperthermia family.
Content updated August 2026.
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