Malignant Hyperthermia: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Malignant Hyperthermia?
An anesthesiologist (a doctor who gives you anesthesia, the medicine that numbs you for surgery) treats an episode. A geneticist (a gene doctor) can help with testing. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is malignant hyperthermia?
Malignant hyperthermia (MH) is a disease. It causes a fast rise in body temperature and severe muscle contractions. It happens when someone receives general anesthesia with certain medicines. These include isoflurane, sevoflurane, desflurane, and succinylcholine. MH is rare. MH is a genetic disorder passed down through families. Hyperthermia means high body temperature. In medicine, the word malignant means dangerous to health. MH is not the same as high body temperature from other medical emergencies such as heat stroke or infection.
People at increased risk are said to have MH susceptibility.
Symptoms
Symptoms of MH can include:
- Muscle rigidity and stiffness.
- A rise in body temperature, which often shows up later and may not be there at the start.
- A fast and often irregular heart rate.
- Abnormally fast breathing.
- Dark brown urine, caused by a muscle protein called myoglobin.
Without fast treatment, the heart and kidneys can stop working.
Causes and who gets it
Changes in the RYR1 and CACNA1S genes increase the risk of MH. Changes in the RYR1 gene account for most cases. In MH, too much calcium is released inside muscle cells. This makes heat and extra acid. It also makes muscles stiff.
MH is inherited. Only one parent has to carry the gene for a child to get it. MH may not happen every time anesthesia is used.
How doctors diagnose it
MH is often found after a person gets anesthesia during surgery. Doctors begin by asking about bad reactions to anesthesia in you and your family. Genetic testing looks for gene changes linked to the disease. Genetic testing should be offered if you or a relative had a severe reaction to anesthesia. A sample of muscle can be tested with caffeine and halothane. This test is reliable but invasive.
Treatment
An MH episode is a medical emergency that needs immediate treatment. The first step is to stop all triggering medicines. The main treatment is dantrolene. It is given through a vein. A cooling blanket can help reduce fever and the risk for serious problems. The person may get fluids through a vein to preserve kidney function. Early diagnosis and fast dantrolene treatment have improved outcomes a lot.
When to see a doctor
Untreated MH episodes can be fatal. Tell your surgeon and anesthesia team if you or a relative had trouble with anesthesia. Also tell them if you have a family history of MH. Avoid stimulant medicines and illicit drugs such as cocaine, amphetamine, and ecstasy. They may cause problems similar to MH in people who are prone to it. Call 911 or go to the emergency room if you have trouble breathing, chest pain, fainting, or a sudden change in mental state.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either type of doctor can write down your family history and help set up genetic counseling. They can also help you share it with your surgical team.
Common questions
Can MH be fatal?
Yes, untreated episodes can be fatal.
Is MH inherited?
Yes, it is a genetic disorder passed down through families. Only one parent has to carry the gene for a child to get it.
Does MH happen every time someone has anesthesia?
No, MH may not occur every time anesthesia is used.
Is MH the same as heat stroke?
No. MH is not the same as high body temperature from other emergencies, such as heat stroke or infection.
What should I tell my surgeon about MH?
Tell your surgeon and anesthesia team before surgery if you or a relative had trouble with anesthesia. Also tell them if you have a family history of MH.
Sources
- MedlinePlus - Malignant hyperthermia
- MedlinePlus Genetics - Malignant hyperthermia
- NORD - Malignant Hyperthermia
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
