Gene affected: SNC4A
Transmission: Autosomal dominant incomplete
Mutation: EquCab3.0 11 g.15474228C>G c.4248C>G
OMIA link: 000785-9796

Breeds: Quater horse

Symptoms:
Hyperkalemic periodic paralysis is a muscle disease seen in horses of American Quater Horse descent and is caused by a dominant incomplete penetrance mutation in the SNC4A gene. The symptoms of HYPP are muscle spasms and paralysis associated with increased serum potassium concentration. Seizures are observed following changes in diet, fasting, stress or consumption of hay, alfalfa rich in potassium.

References:
Aleman, M., Scalco, R., Malvick, J., Grahn, R.A., True, A., Bellone, R.R. (2022) Prevalence of genetic mutations in horses with muscle disease from a neuromuscular disease laboratory. J Equine Vet Sci 118:104129, 2022. Pubmed reference: 36150530. DOI: 10.1016/j.jevs.2022.104129.
Naylor, J.M., Nickel, D.D., Trimino, G., Card, C., Lightfoot, K., Adams, G. (1999) Hyperkalaemic periodic paralysis in homozygous and heterozygous horses: a co-dominant genetic condition Equine Veterinary Journal 31:153-159, 1999. Pubmed reference: 10213428.
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 2:144-147, 1992 Pubmed reference: 1338908. DOI: 10.1038/ng1092-144.um