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Hyperkaliemic Periodic Paralysis (HYPP)


 → Temporary paralysis in Quarter Horses.

Instructions for ordering:

  1. Enter the information of the first horse for which you want to order the test
  2. Add to cart
  3. Go to cart to check out, or
  4. Enter the information for a second horse
  5. For sample collection follow the instructions here.
  6. You can use this template to send in hair samples.
  7. Please also send the completed order form together with the samples.

Please contact us for breeder discount before placing the order.

Any information you include here is optional, but will be included on the certificate of results (except “Additional info”).

Enter the name of your animal
Enter your animal's date/year of birth
Enter the breed name
Enter the registration number if known
Enter the microchip number
Is there anything else you would like to tell us about your horse? Reason for testing, symptoms etc.?

General Information

  • Symptoms can vary strongly in severity.
  • May be life-threatening when heart or lungs are affected by paralysis.
  • Homozygous horses (animals with two copies of the genetic variant) show more severe symptoms than heterozygous individuals (animals with only one copy).
  • Symptoms may occur more frequently after changes in diet, stress or transportation.
  • Inproper signalling between brain and muscles/organs causing the periodic paralysis.
  • Symptoms may be reduced with potassium-deficient diet (avoid Lucerne/Alfalfa in hay)
  • HYPP can be traced back to the sire “Impressive”.


  • General weakness
  • Periodic tremors and paralysis
  • Respiratory problems (noise while breathing)
  • Heavily muscled

Inheritance and Genotypes

→ HYPP is an autosomal dominant hereditary disease, meaning that horses with one or two copies of the genetic variant (n/HYPP or HYPP/HYPP) are affected.

Genotype: The horse is: Effects:
n/n normal. The horse does not have any copies of the genetic variant causative for HYPP and therefore cannot pass it on to any offspring.
n/HYPP affected (heterozygous). The genetic variant causative for HYPP will be passed on to its offspring with a probability of 50%. These 50% will also be affected (n/HYPP).
HYPP/HYPP affected (homozygous). The genetic variant causative for HYPP will be passed on to all offspring. All offspring will also be affected (n/HYPP).


  • Affected animals (n/HYPP or HYPP/HYPP) should not be used for breeding.


Rudolph, J. A., Spier, S. J., Byrns, G., Rojas, C. V., Bernoco, D., & Hoffman, E. P. (1992). Periodic paralysis in quarter horses: a sodium channel mutation disseminated by selective breeding. Nature Genetics, 2(2), 144-147. doi: 10.1038/ng1092-144.

Further information is available at Online Mendelian Inheritance in Animals.

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