Equine Hyperkalemic Periodic Paralysis Disease (HYPP)

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Hyperkalemic Periodic Paralysis Disease (HYPP)


Equine Hyperkalemic Periodic Paralysis Disease (HYPP) is a muscular disease caused by an inherited genetic mutation. HYPP has been traced back to one horse named Impressive and has the alternative name, Impressive Syndrome, named after this horse. Symptoms of HYPP may include muscle twitching, unpredictable paralysis attacks which can lead to sudden death, and respiratory noises. Severity of attacks varies from unnoticeable to collapse or sudden death. The cause of death is usually respiratory failure and/or cardiac arrest.


HYPP is a dominant disorder meaning both homozygous positive (HH) and heterozygous (nH) horses will be affected. Only homozygous negative (nn) horses are not affected by HYPP.


Because HYPP is dominant disorder, the effects of it can also be transposed to other breeds of horses when intermixing occurs. This makes the recognition of this disorder very important in preserving the inherited health of all horses.

Breeds Affected:

Quarter Horse, any horse with Quarter Horse blood.

Additional Tests For Quarter Horses:

Polysaccharide Storage Myopathy (PSSM)

Malignant Hyperthermia (MH)

Hereditary Equine Regional Dermal Asthenia (HERDA)

Glycogen Branching Enzyme Deficiency (GBED)

Combination 5 panel (PSSM, MH, HYPP, HERDA, GBED) $95.00

Test Results:

Animal Genetics offers DNA testing for Equine Hyperkalemic Periodic Paralysis Disease (HYPP). The genetic test verifies the presence of the recessive HYPP gene and presents results as one of the following:

H/H Affected Positive for dominant HYPP gene, indicates the animal carries two inherited copies. Homozygous HYPP horses are genetically bound to pass the gene to 100% of their progeny when bred and all foals will be HYPP horses.
n/H Affected Both the normal and HYPP alleles were detected. Horse tested heterozygous for HYPP. The horse is affected with the HYPP genetic disorder and there is a 50% chance this horse will pass a HYPP allele to its offspring.
n/n Negative Horse tested negative for the gene mutation that causes HYPP and will not pass on the defective gene to its offspring.

    Submit a Sample for Testing:

    To submit a sample for testing please click on ORDER and download a sample submission form. Then follow the sample collection and submission instructions.


    Cost per sample is $30.00. Please see our Equine Fee Schedule for all equine testing rates.