Medically reviewed by Eland Siddle, PharmD · Last updated July 2026
Malignant hyperthermia (MH) is a rare but life-threatening reaction to certain anesthetic gases and the muscle relaxant succinylcholine. For families with a known history, a natural question arises before any planned surgery: can genetic testing tell us whether our child is at risk?
The short answer is yes. Genetic testing can identify variants associated with MH susceptibility, and a positive result carries real, actionable clinical value. That said, a negative result does not definitively rule out susceptibility, which is an important nuance every family and care team should understand.
What Genes Are Involved in Malignant Hyperthermia?
MH susceptibility is most often linked to variants in two genes:
- RYR1 (ryanodine receptor 1) accounts for the large majority of known causative variants. RYR1 encodes a protein in skeletal muscle cells that regulates calcium release. A pathogenic variant in this gene can cause the muscle to react abnormally to triggering anesthetics.
- CACNA1S is a less commonly implicated gene that encodes a voltage-gated calcium channel subunit in skeletal muscle. Pathogenic variants here are rarer but are well-established as MH-associated.
The genetics of MH susceptibility follow an autosomal dominant pattern, meaning a single pathogenic variant inherited from one parent can confer susceptibility. If a parent or sibling has a known causative variant, there is a 50% chance it was passed to each child.
For a deeper background on MH itself, see our companion article: What Is Malignant Hyperthermia?
What Can Genetic Testing Tell You?
A Positive Result
If genetic testing identifies a known pathogenic or likely pathogenic variant in RYR1 or CACNA1S, that is clinically meaningful information. It indicates susceptibility to MH and should be shared with any surgeon, anesthesiologist, or procedural team before surgery, including dental procedures requiring general anesthesia. MH-safe anesthetic protocols exist, and an informed care team can plan accordingly well in advance.
What to do: Inform every healthcare provider involved in future care. Organizations like MHAUS (Malignant Hyperthermia Association of the United States) maintain resources for patients and clinicians, including wallet cards and provider hotlines. Work with a genetic counselor to ensure first-degree relatives are also informed, as they may wish to pursue testing.
A Negative Result and Its Important Limits
A negative genetic test means no known pathogenic variants in the genes tested were detected. For most individuals with no personal or family history of MH, this is reassuring. For someone with a suggestive family history, however, a negative result does not definitively exclude susceptibility.
The reason: not all variants that cause MH susceptibility have been identified. Genetic research continues to characterize the full picture of RYR1 and CACNA1S variants, and in some families the causative variant is not yet known. In this situation, genetic testing alone cannot fully clear someone.
The established diagnostic gold standard for MH susceptibility, particularly when there is a family history and genetic testing is uninformative, is the in vitro contracture test (IVCT), also known as the caffeine-halothane contracture test (CHCT) in North America. This test requires a small biopsy of skeletal muscle, which is then exposed to triggering agents in a laboratory to observe the muscle's response. It is performed at specialized centers and is generally not done in children due to its invasive nature, but it remains the most definitive diagnostic method when genetic results are uncertain.
Positive vs. Negative Result: What It Means and What to Do
| Result | What It Means | Recommended Next Steps |
|---|---|---|
| Positive (known pathogenic variant found) | Confirmed susceptibility to MH. High clinical significance. | Alert all surgical and anesthesia teams before any procedure. Inform first-degree relatives. Consult a genetic counselor and your physician. |
| Negative (no known variant found, no family history) | Lower likelihood of susceptibility. Reassuring in context. | Continue routine surgical care. Mention family history to care teams if relevant. |
| Negative (no variant found, but family history of MH) | Does NOT rule out susceptibility. Causative variant may be unknown. | Discuss IVCT/CHCT with a specialist. Treat anesthesia planning as precautionary until further workup is complete. |
| Variant of uncertain significance (VUS) | A change was detected but its clinical significance is not yet established. | Consult a genetic counselor. Continue precautionary planning. VUS classification may be updated as science advances. |
Why Knowing Before Surgery Matters
The value of knowing a child's MH susceptibility status before any surgical procedure is significant. MH reactions are triggered by specific agents: primarily volatile halogenated anesthetic gases (such as halothane, sevoflurane, and desflurane) and the depolarizing muscle relaxant succinylcholine. None of these agents need to be used, because MH-safe alternatives exist for every step of anesthesia.
When a surgical team knows in advance that a patient carries an MH-susceptibility variant, they can plan a trigger-free anesthetic protocol, ensure dantrolene (the treatment for MH reactions) is immediately available, and monitor appropriately throughout the procedure. This preparation is far easier to arrange proactively than in an emergency. The earlier this information is in a child's medical record, the better.
Where Fore's Screen Fits In
Fore Genomics offers an at-home pediatric genetic health screen using whole genome sequencing, the most comprehensive form of genetic testing available. The screen evaluates more than 1,000 genetic conditions, which includes medically actionable variants in genes like RYR1 and CACNA1S that are associated with conditions such as MH susceptibility.
If a reportable variant in a relevant gene is identified, Fore's board-certified genetic counselors are included with every screen to help families understand the result, discuss its implications, and determine appropriate next steps in coordination with their child's physician. To learn more about what genetic counselors do and why they matter, see our article: What Does a Genetic Counselor Do?
It is important to understand that whole genome sequencing can identify known pathogenic variants when they are present, but it does not guarantee detection of every possible cause of MH susceptibility, consistent with the limitations described above. Results should always be reviewed with a qualified clinician before drawing clinical conclusions.
For parents who want the most comprehensive picture of their child's genetic health from the start, learn more about Fore's screen here.
Personalized Care, Not Prediction
Detecting a risk like malignant hyperthermia early is valuable precisely because it changes what happens in an operating room. Traditional medicine tends to ask: is my child sick? Fore is built around a different question: how do we help keep them healthy? That shift matters, because a genetic finding is not a diagnosis.
- A variant is not a verdict. Most children who carry one will never develop the associated condition.
- It points to personalized care, not a fixed fate. A finding identifies who may benefit from closer attention, not who is destined to get sick.
- It gives your pediatrician a head start. Depending on the finding, that can mean earlier eye or hearing exams, periodic heart monitoring, earlier cholesterol screening, avoiding a specific medication, or simply noting the result to watch over time.
- The goal isn't predicting the future. It's making your child's care more personalized from day one.
Fore's at-home whole genome screen covers 1,000+ conditions and 100+ medication responses, includes board-certified genetic counseling, and reanalyzes your child's genome over time as science advances. See what Fore screens for.
FAQs
Can genetic testing definitively diagnose malignant hyperthermia susceptibility?
A positive genetic test, meaning a known pathogenic variant found in RYR1 or CACNA1S, is considered diagnostically significant and confirms susceptibility. However, a negative genetic test does not definitively rule it out, because not all causative variants have been identified. For individuals with a suggestive family history and a negative genetic result, the in vitro contracture test (IVCT/CHCT) performed at a specialized center is the diagnostic gold standard.
Which genes are tested when looking for malignant hyperthermia risk?
The two primary genes associated with MH susceptibility are RYR1 and CACNA1S. RYR1 accounts for the large majority of known cases. Whole genome sequencing has the ability to evaluate these genes comprehensively, including for variants that targeted panel tests might miss.
If my child tests negative for MH variants, does that mean they are safe for any anesthesia?
A negative result is reassuring, especially in the absence of a family history. However, it does not guarantee safety if there is a known family history of MH, because the specific causative variant in that family may not yet be characterized. Always share relevant family history with your child's anesthesia team regardless of genetic test results.
How would I use a positive genetic test result in practice?
A positive result, meaning a known pathogenic MH-susceptibility variant, should be documented in your child's medical record and communicated to every provider who may administer anesthesia in the future, including dentists and outpatient surgery centers. Your genetic counselor and physician can help you understand how to convey this information effectively and what precautions are standard of care.
At what age should a child be tested if there is a family history of malignant hyperthermia?
There is no single universally agreed-upon age. Many specialists recommend genetic evaluation early, before any elective surgical procedure requiring general anesthesia, so that results can inform planning. A genetic counselor familiar with your family's history is the best resource for timing guidance specific to your situation.