Malignant Hyperthermia (MH)


Malignant Hyperthermia is an autosomal dominant genetic mutation that causes a dog to have dangerous physical reactions in response to specific triggers. The triggers includes exposure to certain drugs, most notably the inhaled anesthetics like halothane. Other triggers include the ingestion of food ingredients such as caffeine and hops and too much exercise. MH is also known as “canine stress syndrome” because the condition can become apparent when a dog is under stress or over-stimulated.


After experiencing one or more of the triggers, an affected dog can have extreme muscle contractions, increased metabolism, rapid heartbeat and elevated body temperature. The body produces too much carbon dioxide, and enters a hypermetabolic state. Muscles become rigid and stiff. Seizures are a possibility.

If a dog with the MH mutation undergoes anesthesia using halothane or other types of inhaled anesthesia, the results can be fatal. However, there are some forms of anesthesia that can be safely used to sedate dogs affected with MH. This is why it is important to identify dogs that have the mutation prior to scheduling surgical procedures. There is no cure for Malignant Hyperthermia, but dogs with this mutation can avoid stressful situations, intense exercise, and food and drugs that trigger symptoms.


The mutation is autosomal dominant; only one copy of the mutation is necessary to produce offspring with MH.

Acceptable Sample Types:

Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Complimentary sample collection kits are available and can be ordered at Canine Test Now.

This Test Is Relevant For the Following Breeds:

Malignant Hyperthermia can be tested for in any breed, but is more prevalent in the following breeds:

  • Border Collie
  • English Springer Spaniel
  • Greyhound
  • Irish Wolfhound
  • Labrador Retriever


Animal Genetics offers DNA testing for Malignant Hyperthermia (MH). The genetic test verifies the presence of the dominant MH mutation and presents results as one of the following:

MH/MH Affected The dog carries two copies of the mutant gene and is homozygous for MH. The dog is affected by Malignant Hyperthermia and will always pass a copy of the mutation to its offspring.
MH/n Affected Both the normal and mutant copies of the gene detected. Dog is affected by Malignant Hyperthermia and can pass on a copy of the defective gene to its offspring.
n/n Clear Dog tested negative for the Malignant Hyperthermia mutation and will not pass on the defective gene to its offspring.