RYR1 rs118204416: Understanding Malignant Hyperthermia Risk
The rs118204416 variant is a specific genetic change within the RYR1 gene that is linked to an increased risk of malignant hyperthermia. This condition is a rare, potentially life-threatening reaction to certain anesthetic medications used during surgery.
What each genotype means
Typical malignant hyperthermia risk
This genotype represents the common, non-pathogenic state for this specific location in the RYR1 gene. It does not carry the specific Arg614Cys mutation associated with malignant hyperthermia susceptibility. Please note that other genetic or environmental factors may still influence your risk profile.
This is the most common genotype found in the general population.
Increased malignant hyperthermia susceptibility
This genotype includes the pathogenic Arg614Cys mutation, which is definitively associated with an increased risk of malignant hyperthermia when exposed to certain volatile anesthetics or depolarizing muscle relaxants. Because this condition is inherited in an autosomal dominant manner, you should inform your healthcare providers and anesthesiologist of this finding before any surgical procedure. Please discuss this result with a genetic counselor or your clinician to understand your specific clinical implications.
This genotype is extremely rare in the general population, typically found only in families with a known history of malignant hyperthermia.
High malignant hyperthermia susceptibility
This genotype indicates the presence of two copies of the pathogenic Arg614Cys mutation. This variant is a well-characterized cause of malignant hyperthermia, a severe reaction to specific anesthetic drugs. You must ensure that all medical and surgical teams are aware of this genetic status prior to any anesthesia, as this is a critical pharmacogenetic finding. Please consult with a medical specialist or genetic counselor to discuss appropriate clinical management.
This genotype is exceptionally rare and is not typically observed in the general population.
What is the rs118204416 Variant?
The rs118204416 variant is a specific alteration in the DNA sequence of the RYR1 gene, often referred to as a missense mutation. In this case, the genetic code is changed such that the amino acid arginine is replaced by cysteine at position 614 in the resulting protein, a change denoted as p.Arg614Cys. This variant is located within a region of the gene that is critical for the proper function of the ryanodine receptor. Because this change can alter the structure of the protein, it is classified as a pathogenic variant in the context of malignant hyperthermia susceptibility. It is important to note that genetic variants are simply differences in DNA sequence; while this specific change is well-characterized in clinical literature, its presence does not mean an individual will experience a reaction, but rather that they may have a higher susceptibility if exposed to specific triggers.
The Role of the RYR1 Gene
The RYR1 gene provides instructions for making a protein called the ryanodine receptor 1. This protein acts as a calcium channel in skeletal muscle cells, playing a vital role in the process of muscle contraction. By controlling the release of calcium ions from the sarcoplasmic reticulum—a specialized storage structure within muscle cells—the ryanodine receptor ensures that muscles contract and relax appropriately in response to nerve signals. When the RYR1 gene contains certain pathogenic variants, this calcium release mechanism can become unstable. In the presence of specific triggers, such as volatile anesthetic gases or the muscle relaxant succinylcholine, the channel may open uncontrollably. This leads to a massive, rapid release of calcium into the muscle cells, causing the hypermetabolic state known as malignant hyperthermia, which is characterized by muscle rigidity, high fever, and rapid heart rate.
Research and Clinical Evidence
The association between RYR1 variants and malignant hyperthermia is well-documented in medical literature. The rs118204416 variant is considered a pathogenic missense mutation, meaning it has been extensively studied and linked to the clinical manifestation of the disorder. Clinical geneticists and expert panels, such as those organized by ClinGen, use rigorous criteria to classify these variants based on their impact on protein function and their presence in affected families. While the evidence for this specific variant is strong, the field of pharmacogenomics continues to evolve as more data is collected. It is important to recognize that the clinical presentation of malignant hyperthermia can be highly variable, even among individuals with the same genetic variant. This variability is due to a combination of genetic, environmental, and physiological factors that are still being actively researched by the scientific community.
Population Frequency and Prevalence
The rs118204416 variant is extremely rare in the general population, with a frequency estimated to be well below 0.01%. Because it is so uncommon, it is not typically found in large-scale, population-wide genetic screening efforts. Instead, this variant is most frequently identified in families that have a known history of malignant hyperthermia. Its rarity means that most people will never encounter this variant. However, for families with a documented history of adverse reactions to anesthesia, genetic testing for this and other RYR1 variants may be recommended by a medical professional. The enrichment of this variant in specific family lineages highlights the importance of family health history in identifying potential risks. If you have concerns about your own risk, the most appropriate step is to consult with a genetic counselor or an anesthesiologist who can review your family history and clinical needs.
Managing Your Genetic Information
Understanding your genetic status regarding the RYR1 gene is a matter of clinical safety rather than a diagnostic label for daily life. If you or a family member are found to carry the rs118204416 variant, this information is primarily used by healthcare providers to plan for safe surgical procedures. It does not mean you have a chronic disease, but it does mean that certain anesthetic agents should be avoided to prevent a potential reaction. You cannot change your genotype, but you can manage your medical care by ensuring that all your doctors, especially your anesthesiologist, are aware of your genetic status before any surgery. Always discuss any genetic test results with a qualified clinician or pharmacist who can help you interpret the findings in the context of your overall health. Never make changes to your medical care or surgical plans based on genetic information without professional guidance.
How common is this variant?
The rs118204416 variant is extremely rare in the general population, occurring at a frequency of less than 0.01%. It is primarily identified in families with a documented history of malignant hyperthermia.
Frequently asked questions
Is rs118204416 a diagnosis for malignant hyperthermia?
No, this variant is a genetic marker associated with susceptibility to malignant hyperthermia. It indicates an increased risk of a reaction to specific anesthetics, not that you currently have the condition.
What should I do if I have this variant?
If you are identified as a carrier, ensure that all your healthcare providers, particularly your anesthesiologist, are aware of this information before any surgery. They can use this knowledge to select safe, alternative anesthetic agents for your care.
How common is this variant in the general population?
The variant is extremely rare, with a frequency of less than 0.01%. It is most commonly found in families with a known history of malignant hyperthermia rather than in the general public.
Can I be tested for this variant?
Yes, genetic testing for RYR1 variants is available, typically through clinical genetics services. It is usually recommended for individuals with a family history of malignant hyperthermia or those who have experienced an unexplained reaction to anesthesia.
Sources & further reading
Educational information only, last refreshed 9/29/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Indicates carrier status for malignant hyperthermia susceptibility type 1 and recessive RYR1-related central core disease.
Well-characterized gain-of-function missense variant predisposing carriers to malignant hyperthermia crisis triggered by volatile inhaled anesthetics.
A variant in the RYR1 gene commonly referenced in clinical and consumer genomics databases.
This pathogenic variant is linked to Central core disease, a congenital myopathy.