Malignant hyperthermia associated with ryanodine receptor 1 (C7360G) mutation in Quarter Horses.
Authors: Aleman M, Nieto J E, Magdesian K G
Journal: Journal of veterinary internal medicine
Summary
# Malignant Hyperthermia in Quarter Horses: A Genetic Risk Beyond the Operating Theatre Malignant hyperthermia (MH) is a pharmacogenetic disorder triggered by certain anaesthetic agents, but a C7360G mutation in the ryanodine receptor 1 gene (RyR1) has previously been documented only in anaesthetised Quarter Horses experiencing life-threatening hypermetabolic crises. This case series examined whether horses carrying the R2454G amino acid substitution could manifest MH symptoms under non-anaesthetic conditions, investigating the broader clinical implications of this genetic mutation. The researchers documented clinical presentations of MH in affected horses outside the anaesthetic setting, demonstrating that the mutation confers a wider disease phenotype than traditionally recognised. For equine practitioners, this finding is critical: horses with known or suspected C7360G mutations require careful management protocols beyond anaesthetic avoidance, as stress, exercise or environmental triggers may precipitate dangerous episodes. Genetic screening of Quarter Horse populations and development of updated clinical guidelines for managing carriers of this mutation are now essential to prevent unexpected crises in performance, breeding and routine veterinary contexts.
Read the full abstract on PubMed
Practical Takeaways
- •Quarter Horse owners and veterinarians should be aware that specific RyR1 mutations predispose to anesthetic complications; genetic testing may identify at-risk individuals before elective surgery
- •Anesthetists working with Quarter Horses should consider MH risk and have appropriate monitoring and emergency protocols in place, particularly if family history or prior anesthetic reactions are noted
- •This mutation represents a significant liability in breeding programs; genetic screening could prevent affected offspring in Quarter Horse populations
Key Findings
- •Quarter Horses carry a C7360G point mutation in RyR1 gene resulting in R2454G amino acid substitution
- •This mutation is associated with anesthetic-induced malignant hyperthermia in Quarter Horses
- •No previous reports existed of nonanesthetic manifestations of MH in horses with the C7360G mutation