MH Malignant hyperthermia

• 30 to 40 - hair roots - envelope

• 5 mL - blood - K3 EDTA tube

Turnaround time

• 2 to 5  working days

Results description

The DNA test verifies the presence of the dominant MH gene and presents results as one of the following:

• N/ - Negative for MH.  Absence of the allele responsible for Malignant Hyperthermia (MH).
• MH/N - Affected - Positive heterozygous for MH. Presence of one copy of the allele responsible for MH. The horse is affected with the MH disorder and can pass the MH allele  to 50% of their progeny when bred.
• MH/ - Affected - Positive homozygous for MH. Presence of two copies of the allele responsible for MH.  The horse is affected with the MH disorder and will pass the MH allele to 100% of its offspring.

Additional information

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 anaesthesia 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 anaesthesia. Horses that are known to have the MH mutation can be given medication prior to administering anaesthesia to help reduce the severity of the symptoms.