Malignant Hyperthermia

Malignant hyperthermia (MH) is disease passed down through families that causes a fast rise in body temperature (fever) and severe muscle contractions when the affected person gets general anesthesia. This condition is not the same as hyperthermia that is due to medical emergencies such as heat stroke or infection.


Symptoms can include:

  • Bleeding
  • Dark brown urine
  • Muscle ache without an obvious cause, such as exercise or injury
  • Muscle rigidity and stiffness
  • Quick rise in body temperature

Myotonia of the eyelid (a disorder causing the inability to relax voluntary muscle after vigorous effort).


The use of certain medicines can prevent complications from malignant hyperthermia during surgery. In addition, avoiding the use of stimulant drugs such as cocaine, amphetamines and ecstasy as they can produce problems similar to MH in those persons who are predisposed to this condition.

Genetic testing is recommended for those persons who have a family history of myopathy, muscular dystrophy or malignant hyperthermia.

Gene or region studied

  • RYR1
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