Hipertermia maligna - HM
Prueba de ADN para la hipertermia maligna (HM). Esta prueba verifica la presencia del gen MH dominante y presenta resultados como...
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Acerca de la prueba
Esta prueba de ADN detecta la Hipertermia Maligna (HM) mutación, un trastorno genético hereditario que afecta la función del músculo esquelético en caballos Quarter y razas relacionadas.
La prueba identifica si un caballo está libre o afectado por la mutación dominante de HM, apoyando las decisiones de cría y el manejo clínico antes de la anestesia o el ejercicio intenso.
¿Por qué probar?
Esta prueba genética ayuda a:
- Identificar caballos portadores de la mutación dominante MH.
- Apoyar decisiones responsables de cría.
- Evaluar el riesgo de hipertermia maligna antes de la anestesia.
- Identificar caballos con mayor riesgo de crisis musculares inducidas por ejercicio o estrés.
- Detectar caballos que también pueden beneficiarse de pruebas adicionales PSSM1 .
Signos clínicos
Signs usually appear in adult horses. Two kinds of attack are on record.
Attacks under anaesthesia:
- Body temperature climbing fast, recorded between 40 and 45 degrees Celsius. In one monitored case it rose about 0.12 degrees every minute.
- A racing heart that loses its rhythm, and high blood pressure
- Heavy sweating. The anaesthetic tubing becomes hot to the touch.
- Muscles locking up: first in one place, such as the ears drawn in or the jaw clamped shut, then all over, with the third eyelid showing and the eye pulled back into the socket
- The blood turning acid, with carbon dioxide building up even though the horse is on a ventilator with pure oxygen
- Blood salts out of balance, thickened blood, high blood sugar, struggling kidneys and muscle breakdown products rising fast
- Death, with the body stiffening unusually quickly afterwards
Attacks with no anaesthetic involved:
- Severe, sudden muscle breakdown with a body temperature recorded between 40.2 and 43.3 degrees Celsius
- Episodes that look like colic, locked muscles, a stiff way of going, tiring quickly, sweating on and off, a fast heart and fast breathing
- Extremely high muscle enzymes on a blood test, and acid blood
- Muscle enzymes that stay raised between attacks, in horses that otherwise look well
- Sudden death, including death out in the field on an unusually hot day
What sets off an attack: every gas anaesthetic of the halogenated family (halothane, isoflurane, desflurane, sevoflurane) and muscle relaxants such as succinylcholine. Also exercise, the stress of transport or a new place, the start of training, the excitement of breeding, extreme heat, and another illness or muscle disease at the same time.
An attack is a veterinary emergency. What is reported to save horses: spotting it early, stopping the anaesthetic gas or muscle relaxant at once, cooling the body actively, and giving dantrolene.
None of these signs is unique to MH. They also happen under anaesthesia and after hard work for other reasons. Your veterinarian makes the diagnosis from the history, the examination, blood results and this genetic result.
Transmisión
MH 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. Through a positive parent, the variant can pass into other breeds and lines.
What each mating can produce:
- n/n x n/n gives 100% n/n
- n/n x n/MH gives 50% n/n, 50% n/MH
- n/MH x n/MH gives 25% n/n, 50% n/MH, 25% MH/MH
No horse with two copies has been found yet. The researchers put this down to how rare the disease is, not to any evidence that two copies would be lethal.
Prevención
There is no cure. The result guides two things.
Managing a positive horse. This part saves lives, and it belongs to your veterinarian:
- Ask your veterinarian to record the result in the horse's clinical file, so it is known before any general anaesthesia and in an emergency
- Medication can be given before anaesthesia to reduce the severity of an attack
- Avoid the other triggers listed under Clinical signs where you can
- A horse that also carries PSSM1 needs that condition managed as well
Breeding. Breeding from positive horses is discouraged. Test breeding stock before mating, and if a positive horse is used, choose a partner that tested negative.
Resultados
La prueba de ADN verifica la presencia del gen dominante MH y presenta los resultados como uno de los siguientes:
- N/ - Negativo para MHAusencia del alelo responsable de la Hipertermia Maligna (MH).
- MH/N - Afectado - Positivo heterocigoto para MHPresencia de una copia del alelo responsable de MH. El caballo está afectado por el trastorno MH y puede transmitir el alelo MH al 50% de su descendencia cuando se reproduce.
- MH/ -Afectado - Positivo homocigoto para MHPresencia de dos copias del alelo responsable de MH. El caballo está afectado por el trastorno MH y transmitirá el alelo MH al 100% de su descendencia.
Requisitos de muestra
30 a 40 - raíces del cabello - sobre o 5 mL - sangre - 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.
¿Por qué debería hacerme la prueba de Hipertermia Maligna?
La prueba identifica caballos portadores de la mutación de HM, permitiendo decisiones informadas de cría y ayudando a los veterinarios a reducir riesgos anestésicos mediante un manejo adecuado.
¿Qué caballos son los más comúnmente afectados?
La mutación se encuentra principalmente en Quarter Horses y razas relacionadas, aunque la prueba puede ser apropiada siempre que haya un pedigrí relevante o sospecha clínica.
¿Debería también hacer la prueba de PSSM1?
Sí. Los caballos portadores de ambas HM y PSSM1 pueden desarrollar signos clínicos más severos, por lo que se recomienda la prueba para ambas condiciones en razas susceptibles.
¿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: RYR1 (ryanodine receptor 1), ECA10.
- Variant: missense Arg to Gly. HGVS (EquCab3.0): NC_009153.3:g.9678680C>G; XM_023649662.1:c.7363C>G; XP_023505430.1:p.(Arg2455Gly).
- Alternative designations: published as c.7360C>G, p.(Arg2454Gly) (R2454G; Aleman et al., 2004). OMIA restates it against transcript XM_023649662.1, giving c.7363C>G and R2455G; both designations refer to the same genomic change. Laboratories differ in which they print, so quote both when comparing reports.
- Discovery: candidate-gene approach from the homologous disease in pigs and humans; the change was found in two affected horses (Aleman et al., 2004). The homologous position is altered in two of the five known human malignant hyperthermia susceptibility types.
- Mechanism: RYR1 encodes the calcium release channel of skeletal muscle. In susceptible horses the channel can be forced open, flooding the cell with calcium; hypermetabolism follows, with intense heat production and acidosis, and often death.
- Variant identifiers: no rs/EVA identifier listed in OMIA; OMIA variant 159.
- Variant classification: not currently evaluated (ISAG/AVCG, per OMIA).
- Inheritance: autosomal dominant (OMIA code D), inferred from two heterozygous affected horses; no formal pedigree analysis has been published (Aleman et al., 2004, as cited in OMIA).
- Penetrance / expressivity: estimated mortality 34% in susceptible horses under halothane anaesthesia (Aleman et al., 2009). PSSM phenotype is more severe in horses carrying both RYR1 and GYS1 variants (McCue et al., 2009).
- Breeds with documented carriers or cases: Quarter Horse, Appaloosa, American Paint Horse (OMIA variant record). All horses in the first clinical series were Quarter Horses of halter lines. The clinical syndrome has also been reported in Thoroughbreds, Arabians and ponies, not all attributed to this variant.
- Allele / carrier frequencies: among 159,227 horses of 16 breeds, the variant was found in 391 Quarter Horses, 18 Paint Horses, 1 Appaloosa and 1 Quarter Horse x Clydesdale; allele frequency 0.13% in Quarter Horses and 0.12% in Paint Horses and Appaloosas (Aleman, McCue and Bellone, 2025).
- Clinical notes for veterinarians: consider concurrent GYS1 (PSSM1) testing in Quarter Horse-related breeds.
Key references:
- Aleman M, Riehl J, Aldridge BM, LeCouteur RA, Stott JL, Pessah IN (2004). Association of a mutation in the ryanodine receptor 1 gene with equine malignant hyperthermia. Muscle Nerve 30:356-365. doi:10.1002/mus.20084. PMID 15318347.
- Aleman M, Nieto JE, Magdesian KG (2009). Malignant hyperthermia associated with ryanodine receptor 1 mutation in Quarter Horses. J Vet Intern Med 23:329-334. doi:10.1111/j.1939-1676.2009.0274.x.
- McCue ME, Valberg SJ, Jackson M, Borgia L, Lucio M, Mickelson JR (2009). Polysaccharide storage myopathy phenotype in Quarter Horse-related breeds is modified by the presence of an RYR1 mutation. Neuromuscul Disord 19:37-43. doi:10.1016/j.nmd.2008.10.001.
- Aleman M, McCue M, Bellone RR (2025). Allele frequencies and genotypes for the ryanodine receptor 1 variant causing malignant hyperthermia and fatal rhabdomyolysis with hyperthermia in horses. J Vet Intern Med 39:e70081. doi:10.1111/jvim.70081.
- Sperandio LMS, Lago GR, Albertino LG, Araujo CET, Ferreira C, Borges AS, Oliveira-Filho JP (2024). Allele frequency of muscular genetic disorders in bull-catching (vaquejada) Quarter Horses. J Equine Vet Sci 136:105052. doi:10.1016/j.jevs.2024.105052.