Equine Malignant Hyperthermia (MH)

Malignant Hyperthermia or MH is a genetic muscle disorder that affects Quarter Horses and related breeds.  Horses with the MH mutation may not show any physical signs of the disorder until triggered by exposure to anesthesia or extreme exercise or stress.  Symptoms can include high temperature, increased heart rate, high blood pressure, sweating, acidosis, and muscle rigidity.  Symptoms develop rapidly, and if not treated quickly, this condition can be fatal.

MH is inherited as an autosomal dominant trait, so the disorder can be passed on even if only one parent has the defective gene.  The mutation can be present along with PSSM, and if a horse also has PSSM, the symptoms associated with MH can be more severe. Therefore, testing for both PSSM and MH is recommended for Quarter Horse breeds.

Although this condition is rare, testing for MH is recommended in case a horse must undergo anesthesia.  Horses that are known to have the MH mutation can be given medication prior to administering anesthesia to help reduce the severity of the symptoms.

Animal Genetics offers testing for MH. The cost is $35.00 and the turnaround time is 2-4 business days.  We also test for MH as part of a panel which includes testing for HERDA, HYPP, GBED, and PSSM. The price for the panel is $95.00. Visit our website’s Malignant Hyperthermia page for more information about our test, sample collection guidelines, and a link to the submission form.

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