We have changed our visitation policy for the safety of our patients and staff. Click here for the updated visitation policy and click here for information about COVID-19.

Lahey Health is now part of Beth Israel Lahey Health

(Malignant hyperpyrexia; Malignant Hyperthermia Susceptibility)


Malignant hyperthermia (MH) is a fast and harmful rise in body temperature.


This problem is often caused by a faulty gene. People who have the gene have malignant hyperthermia susceptibility.

MH can be triggered by certain medicines, mainly anesthesia and muscle relaxers.

Risk Factors

This problem is more common in young adults and men. Having others in the family with this problem also raises the risk a person will have it.


Problems may start after medicine is given. A person may have:

  • Fever higher than 105 degrees Fahrenheit (ºF) (40.6 degrees Celsius [ºC])
  • Stiff muscles
  • Muscle spasms, mainly in the face
  • Fast breathing
  • Fast or irregular heartbeat
  • Dark urine
  • An uneven skin color
Muscle Fibers
Copyright © Nucleus Medical Media, Inc.


MH is an emergency. It is diagnosed based on symptoms and recent anesthesia.

MH susceptibility may be suspected based on a person's medical and family history. Genetic testing and a muscle biopsy may be done to confirm it.


Any medicine causing this problem will be stopped or changed. Medicine may also be given to lower body temperature.

Emergency care will be needed, such as:

  • Oxygen therapy
  • Ending or postponing surgery
  • Supportive care and monitoring


A person with MH susceptibility or a family history of MH should share this information with their doctors, mainly before any surgery or procedure.


American Association of Neuromuscular and Electrodiagnostic Medicine  http://aanem.org 

Malignant Hyperthermia Association of the United States  http://www.mhaus.org 


Canadian Organization for Rare Disorders  http://www.raredisorders.ca 

Health Canada  https://www.canada.ca 


FAQs: General MH questions. Malignant Hyperthermia Association of the United States website. Available at: http://www.mhaus.org/faqs/category/frequently-asked-questions-about/about-mh/. Accessed December 3, 2019.

Malignant hyperthermia. American Association of Neuromuscular and Electrodiagnostic Medicine website. Available at: http://aanem.org/Patients/Disorders/Malignant-Hyperthermia. Accessed December 3, 2019.

Malignant hyperthermia. EBSCO DynaMed website. Available at:  https://www.dynamed.com/condition/malignant-hyperthermia . Updated March 4, 2016. Accessed December 3, 2019.

Rosenberg H, Pollock N, et al. Malignant hyperthermia: a review. Orphanet J Rare Dis. 2015 Aug 4;10:93.

Revision Information

  • Reviewer: EBSCO Medical Review Board James P. Cornell, MD
  • Review Date: 09/2019
  • Update Date: 05/06/2020