--- license: permission_granted topic_id: companion_species_health_hyperkalemic_periodic_paralysis_hypp_horse category: companion-species-health title: "Horse (Equus caballus) — Hyperkalemic Periodic Paralysis (HYPP) (hereditary; OMIA-verified species predisposition)" lang: en source: "OMIA (Online Mendelian Inheritance in Animals, University of Sydney) species-specific hereditary-disorder record, saved verbatim to source_file; C1 substring-verified. Pulled 2026-08-24 from local OMIA database dump." source_file: pdf-raw/species-health/horse_hyperkalemic_periodic_paralysis_hypp_61.txt date_parsed: 2026-08-24 tokens_estimated: 570 verification: method: substring_match claims: 6 passed: 6 date: 2026-08-24 recovered: false path: companion-species-health/companion_species_health_hyperkalemic_periodic_paralysis_hypp_horse/01_companion_species_health_hyperkalemic_periodic_paralysis_hypp_horse.md source_document: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" citation: authority: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" title: "Horse (Equus caballus) — Hyperkalemic Periodic Paralysis (HYPP) (hereditary; OMIA-verified species predisposition)" url: "https://omia.org/OMIA000785/9796/" retrieved: "2026-08-24" ref: "OMIA species-specific hereditary-disorder records (omia.org), derived from local OMIA database dump; dataset: https://doi.org/10.25910/2AMR-PV70" doc_type: "academic animal-genetics database (species-specific disorder entries)" needs_review: false
verification_derived: method: derived_from_dataset source: "OMIA database dump (omia.xml, local); fields Gene/Variant/Article/OMIM" note: "Structured fields (gene, variant rsID/protein change, PubMed/DOI references, OMIM cross-link) extracted from OMIA dump and presented with first-hand values; not verbatim prose."---
Horse (Equus caballus) — Hyperkalemic Periodic Paralysis (HYPP) (hereditary; OMIA-verified species predisposition)
Source: first-hand OMIA (University of Sydney) species-specific hereditary-disorder record, saved verbatim to source_file; every claim below is a C1 byte-substring of it.
Claims
Species: Horse (Equus caballus)Disorder: Hyperkalemic Periodic Paralysis (HYPP)Mode of inheritance: Naylor et al. (1999) compared the clinical responses of heterozygotes to homozygotes for the variant causing HYPP and determined that homozygotes are more severely affected, demonstrating the partial dominant mode of inheritance. {text supplied by Professor E. Bailey and students; 20 March 2019}Summary: HYPP in horses is an autosomal incompletely dominant disorder characterized by episodic attacks of muscle tremors, weakness and paralysis with associated increased serum potassium concentration (Rudolph et al., 1992; Animal Genetics). While HYPP is considered a defect by the American Quarter Horse Association (AQHA), some breeders consider the muscular phenotype attractive and select for this phenotype. Thus, the AQHA refuses to register homozygous animals, but still registers heterozygotes. {with thanks to Tatyana German and Meredith O’Connell, working under the guidance of Professor Ernie Bailey; 15 Feb 2019}Clin feat: Muscle fasciculation and spasm; weakness; recumbency; episodic attacks of muscle tremors, weakness and paralysis with associated increased serum potassium concentration; pronounced muscularity; attacks follow diet changes, fasting, stressful circumstances or after consumption of alfalfa hay which is high in potassium (Steiss & Naylor 1986; Spier et al., 1990) {with thanks to Tatyana German and Meredith O’Connell, working under the guidance of Professor Ernie Bailey; 15 Feb 2019}Prevalence: Quarter Horse; Bowling et al. (1996) reported that all horses possessing the variant were descendants of a “Stallion 1” subsequently identified as IMPRESSIVE, born in 1969. Tryon et al.( 2009) tested subpopulations of Quarter Horses and found the variant absent among cutting horses, cow horses, reining horses and racing horses. It was present among barrel racing horses (allele frequency 0.006), western pleasure horses (allele frequency 0.013) and halter horses (allele frequency 0.299). The variant was also found among paint horses that were crosses from Quarter Horse. {with thanks to Tatyana German and Meredith O’Connell, working under the guidance of Professor Ernie Bailey; 15 Feb 2019}
Associated gene(s)
Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.
- Gene: Entrez Gene ID 4153124 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
- OMIA molecular-genetics note: The molecular basis of this disorder was first reported by Rudolph et al. (1992, Nature Genetics). Having established that the horse gene for adult skeletal muscle sodium channel (SNC4A) is completely linked with this disorder (see Mapping section above), Rudolph et al. (1992, Nature Genetics) identified the causative mutation as a missense mutation causing an amino acid substitution from phenylal…
Evidence (references)
Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.
- 1992. Linkage of Hyperkalaemic Periodic Paralysis in Quarter Horses to the Horse Adult Skeletal Muscle Sodium Channel Gene. Animal Genetics — PubMed:PMID1323940 — OMIA Phene_Article / Article
- 1992. Inheritance of Myotonic Discharges in American Quarter Horses and the Relationship to Hyperkalemic Periodic Paralysis. Canadian Journal of Veterinary Research - Revue Canadienne de Recherche Veterinaire — PubMed:PMID1586896 — OMIA Phene_Article / Article
- 1992. Familial Incidence of Hyperkalemic Periodic Paralysis in Quarter Horses. Journal of the American Veterinary Medical Association — PubMed:PMID1548168 — OMIA Phene_Article / Article
- 1992. Periodic Paralysis in Quarter Horses - A Sodium Channel Mutation Disseminated by Selective Breeding. Nature Genetics — PubMed:PMID1338908 | DOI:10.1038/ng1092-144 — OMIA Phene_Article / Article
- 1993. Genetic Study of Hyperkalemic Periodic Paralysis in Horses. Journal of the American Veterinary Medical Association — PubMed:PMID8468218 — OMIA Phene_Article / Article
- 1993. Clinical Syndrome and Diagnosis of Hyperkalaemic Periodic Paralysis in Quarter Horses. Equine Veterinary Journal — PubMed:PMID8508753 — OMIA Phene_Article / Article
- 1993. Blood Test Available for Hyperkalemic Periodic Paralysis in Quarter Horses. Journal of Equine Veterinary Science — OMIA Phene_Article / Article
- 1993. Hyperkalaemic Periodic Paralysis - Diagnosing the Disease in the Headlines. Equine Veterinary Journal — PubMed:PMID8508741 — OMIA Phene_Article / Article
- 1993. Phenytoin Increases Specific Triacylglycerol Fatty Esters in Skeletal Muscle from Horses with Hyperkalemic Periodic Paralysis. Biochimica et Biophysica Acta — PubMed:PMID8323969 — OMIA Phene_Article / Article
- 1994. Selection of Quarter Horses Affected with Hyperkalemic Periodic Paralysis by Show Judges. Journal of the American Veterinary Medical Association — PubMed:PMID8188514 — OMIA Phene_Article / Article
- 1994. Equine Hyperkalemic Periodic Paralysis - Review and Implications. Canadian Veterinary Journal - Revue Veterinaire Canadienne — OMIA Phene_Article / Article
- 1994. Hyperkalemic Periodic Paralysis in Horses .2. Magyar Allatorvosok Lapja — OMIA Phene_Article / Article
- (36 additional references in OMIA)
Comparative medicine (human OMIM)
Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.
- OMIM:170500 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
- OMIM:603967 (type: gene) — OMIA Group_OMIM (via OMIA_ID)
- OMIM:613345 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
- OMIM:614198 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
- OMIM:608390 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
- OMIM:168300 (type: trait) — OMIA Group_OMIM (via OMIA_ID)