Parálisis periódica hiperpotasémica - HYPP
Prueba de ADN para la enfermedad de parálisis periódica hiperpotasémica (HYPP). Esta prueba de ADN verifica la presencia del gen HYPP...
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Acerca de la prueba
Esta prueba de ADN verifica la presencia del Parálisis Periódica Hipercalémica (HYPP) variante genética.
¿Por qué probar?
Esta prueba genética ayuda a los criadores a identificar caballos portadores de la variante genética HYPP, permitiendo decisiones de cría informadas y ayudando a prevenir el nacimiento de potros afectados.
Todos los descendientes de Impressive deben ser examinados para HYPP.
Debido a que HYPP es un trastorno dominante, la mutación también puede presentarse en otras razas de caballos mediante cruces.
También se recomienda realizar la prueba en caballos que muestren signos clínicos compatibles con HYPP.
Signos clínicos
Attacks come and go and vary a lot from horse to horse, from barely noticeable to collapse or sudden death. Between attacks the muscles work normally.
- Muscle twitching and trembling, sometimes continuous, that can progress to weakness, paralysis and the horse going down
- The horse stays conscious and does not seem to be in pain
- Spasm of the face muscles, the third eyelid sliding across the eye, drooling, and sweating while body temperature stays normal
- Noisy breathing and blue gums as the throat muscles go slack and block the airway; trouble swallowing and a changed whinny
- Heavy, well-developed muscling, sometimes very marked
- Tiring quickly in work; attacks that can look like colic or staggering, or leave the horse sitting like a dog
- In severe attacks, an abnormal heart rhythm and sudden death
- Attacks often follow a change of feed, a period without food, a stressful event or a meal rich in potassium
None of these signs is unique to HYPP, and HYPP is not the same as tying up, colic or a seizure. Your veterinarian decides whether a horse is ill, using the history, the examination, blood results and this result.
Transmisión
HYPP is dominant. One copy is enough to make a horse susceptible. The gene is not on a sex chromosome, so colts and fillies are affected equally.
What each mating can produce:
- n/n x n/n gives 100% n/n
- n/n x n/H gives 50% n/n, 50% n/H
- n/n x H/H gives 100% n/H
- n/H x n/H gives 25% n/n, 50% n/H, 25% H/H
- n/H x H/H gives 50% n/H, 50% H/H
- H/H x H/H gives 100% H/H
Prevención
There is no cure. The result guides two things.
Breeding. Only a mating between two horses that tested negative is sure to give no affected foals. Breeding from positive horses is not recommended.
Managing a positive horse. The measures reported are:
- A diet low in potassium, with grass hay rather than alfalfa
- Regular smaller meals instead of large irregular ones, and no sudden changes of feed
- Salt available at all times
- Daily exercise and turnout instead of long spells in a stable
- Telling your veterinarian and anaesthetist the result before any operation, because general anaesthesia can set off an attack
Some medicines that make the horse pass more urine have been reported to make attacks less frequent and less severe. Horses with two copies have been managed with medical and surgical treatment. Your veterinarian sets the diet, monitoring and any treatment.
Resultados
La prueba de ADN verifica la presencia del gen recesivo HYPP y presenta los resultados como uno de los siguientes:
- N/ – Normal - Ausencia del alelo responsable de HYPP.
- N/H – Afectado - Heterocigoto positivo para HYPP. Presencia de una copia del alelo responsable de HYPP. El caballo está afectado por el trastorno HYPP y hay un 50% de probabilidad de que este caballo transmita un alelo HYPP a su descendencia.
- H/ – Afectado - Homocigoto positivo para HYPPPresencia de dos copias del alelo responsable de HYPP. El caballo está afectado por el trastorno HYPP y hay un 100% de probabilidad de que este caballo transmita un alelo HYPP a su descendencia.
Requisitos de muestra
30 a 40 raíces de cabello o 5 mL de sangre en tubo K3 EDTA
Envía tu muestra por correo ordinario o entrega exprés a:
Laboratorio Equigerminal HIESE
Rua da Quinta do Sobreiro Nº25
3230-343 Penela, Portugal
Tiempo de entrega
2 a 5 días hábiles
Cómo funciona
🛒 Compra el Test: Selecciona y compra el test en línea.
📧 Recibe Instrucciones: Después de la confirmación del pago, recibe instrucciones para la recolección de la muestra.
✨ Recolección de Muestras: Tu veterinario recoge raíces de cabello o una muestra de sangre.
📄 Descarga el Formulario de Envío: Descarga el formulario de envío imprimible.
📮 Envía las Muestras: Envía tus muestras por correo ordinario o entrega exprés a:
Equigerminal Lab HIESE
Rua da Quinta do Sobreiro Nº25
3230-343 Penela, Portugal
📄 Recibe Resultados: Recibe tu certificado de resultados por correo electrónico.
Preguntas frecuentes
¿Qué muestras se pueden enviar?
La prueba se puede realizar utilizando 30–40 raíces de cabello o 5 mL de sangre recogida en un tubo K3 EDTA.
¿Qué caballos deben ser analizados?
Se recomienda realizar la prueba a todos los descendientes de Impressive, caballos destinados a la reproducción y caballos que muestren signos clínicos compatibles con HYPP.
¿Qué significan los resultados?
N/N: El caballo no tiene la mutación HYPP.
N/H: El caballo está afectado y tiene un 50% de probabilidad de transmitir la mutación a su descendencia.
H/H: El caballo está afectado y transmitirá la mutación a toda su descendencia.
¿Es HYPP un trastorno recesivo?
No. Aunque el texto original se refiere incorrectamente a un gen recesivo en algunos lugares, HYPP es un trastorno genético dominante. Tanto N/H como H/H los caballos están afectados, mientras que solo los N/N no están afectados.
¿Cuánto tiempo tarda en recibirse los resultados?
Los resultados están disponibles en 2 a 5 días hábiles después de la llegada de la muestra al laboratorio.
For Professionals
Genetic and clinical detail for veterinarians, geneticists and laboratories.
- Gene / locus: SCN4A (sodium voltage-gated channel alpha subunit 4, skeletal muscle), ECA11.
- Variant: F1416L (Phe1416Leu), missense. HGVS (EquCab3.0): NC_009154.3:g.15474228C>G; NM_001081761.1:c.4248C>G; NP_001075230.1:p.(Phe1416Leu).
- Alternative designations: H allele (OMIA allele symbol); Impressive syndrome, after the founder stallion.
- Variant identifiers: rs1148998534 (EVA); OMIA variant 162.
- Variant classification: not currently evaluated (ISAG/AVCG, per OMIA).
- Mechanism: impaired sodium channel inactivation (Cannon et al., 1995). Persistent sodium influx leaves the muscle membrane hyperexcitable. The defect is unmasked by rises in serum potassium, which links episodes to feeding.
- Evidence of causality: complete co-segregation of SCN4A with HYPP in families (Rudolph et al., 1992b), followed by identification of the causal variant (Rudolph et al., 1992a). This was the first equine disease with an identified causal variant.
- Inheritance: autosomal incomplete dominant (OMIA code AID); homozygotes more severely affected than heterozygotes, described as co-dominant (Naylor et al., 1999).
- Penetrance / expressivity: variable; most affected horses show no signs until mature and in training.
- Breeds with documented carriers or cases: Quarter Horse (OMIA variant record), Quarter Horse crosses including Appendix Quarter Horses, and American Paint Horses of Quarter Horse descent. All carriers traced to a single founder, the Quarter Horse stallion Impressive, born 1969 (Bowling et al., 1996). The variant spread through selection for heavy muscling. The Appaloosa is not listed because no source was found.
- Allele / carrier frequencies: allele frequency by discipline in American Quarter Horses (Tryon et al., 2009; 651 elite performance and 200 control horses): 0% in cutting, working cow, reining and racing; 0.6% in barrel racing; 1.3% in western pleasure; 29.9% in halter; 0.8% in the general Quarter Horse population. Allele frequency 31.8% in halter horses, with no change over time in the random cohort (Brown et al., 2026; 300 performance horses across seven disciplines and 300 random Quarter Horses born 2020 to 2024).
- Homozygote phenotype: in Naylor et al. (1999), all 9 H/H horses had respiratory stridor, usually within the first week of life; 5 had dysphagia, 3 ptyalism and 3 weight loss. Six of the 9 died or were euthanised (4 before one year, 1 at 20 months, 1 at five years). Of 35 contemporaneous half siblings, 1 had stridor before weaning and none had dysphagia. On potassium challenge, H/H horses showed ptyalism, third eyelid prolapse, stridor and weakness far more often than n/H horses.
- Clinical / diagnostic notes for veterinarians: the DNA test has replaced potassium challenge (false negatives) and electromyography (abnormalities not specific to HYPP). Muscle biopsy is not diagnostic for HYPP but can help exclude other myopathies. Hyperkalaemia has other causes, and serum potassium can be falsely raised by the sample itself. The American Quarter Horse Association treats HYPP as a defect, does not register H/H horses and registers n/H horses.
Key references:
- Rudolph JA, Spier SJ, Byrns G, Rojas CV, Bernoco D, Hoffman EP (1992a). Periodic paralysis in Quarter Horses: a sodium channel mutation disseminated by selective breeding. Nat Genet 2:144-147. doi:10.1038/ng1092-144. PMID 1338908.
- Rudolph JA, Spier SJ, Byrns G, Hoffman EP (1992b). Linkage of hyperkalaemic periodic paralysis in Quarter Horses to the horse adult skeletal muscle sodium channel gene. Anim Genet 23:241-250.
- Cannon SC, Hayward LJ, Beech J, Brown RH Jr (1995). Sodium channel inactivation is impaired in equine hyperkalemic periodic paralysis. J Neurophysiol 73:1892-1899.
- Naylor JM, Nickel DD, Trimino G, Card C, Lightfoot K, Adams G (1999). Hyperkalaemic periodic paralysis in homozygous and heterozygous horses: a co-dominant genetic condition. Equine Vet J 31:153-159.
- Bowling AT, Byrns G, Spier S (1996). Evidence for a single pedigree source of the hyperkalemic periodic paralysis susceptibility gene in Quarter Horses. Anim Genet 27:279-281.
- Tryon RC, Penedo MCT, McCue ME, Valberg SJ, Mickelson JR, Famula TR, Wagner ML, Jackson M, Hamilton MJ, Nooteboom S, Bannasch DL (2009). Evaluation of allele frequencies of inherited disease genes in subgroups of American Quarter Horses. J Am Vet Med Assoc 234:120-125. doi:10.2460/javma.234.1.120.
- Brown BN, Hughes S, Le TM, Tatar NP, Grahn JC, Carrillo-Alvarez M, Bellone RR, Finno CJ (2026). Allele frequencies of 7 inherited disorders in performance and random cohorts of American Quarter Horses (2020-2024). J Am Vet Med Assoc 1-7. doi:10.2460/javma.26.04.0256.