Breeds Affected: Quarter Horse and related breeds
Samples Accepted: Blood, Hair
Disease Information: Hyperkalemic Periodic Paralysis (HYPP) is a potential fatal disease which may result in collapse, paralysis, and/or respiratory distress. Disease severity is variable, and in some animals may only show a difficulty recovering from exercise, due to muscle damage.
Inheritance Information: HYPP is incomplete autosomal dominant, meaning that animals with only one copy of this allele will be affected, and will pass it on to 50% of its offspring.
The possible genotypes are:
N/N The horse is normal, and cannot produce HYPP-affected offspring.
N/hypp The horse is a carrier of HYPP, and can pass the allele on to approximately 50% of any offspring. There is a greater risk of being affected by itself.
hypp/hypp The horse is affected with HYPP. If bred to another horse (N/N or N/h) 100% of the offspring will be affected.
– Carriers (N/hypp) and affected animals (hypp/hypp) should not be used for breeding.
Test Information: This test is based on a mutation in the SCN4A gene.
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 the Online Mendelian Inheritance in Animals website.