Malignant Hyperthermia Associated with Ryanodine Receptor 1 (C7360G) Mutation in Quarter Horses
Article first published online: 11 FEB 2009
Copyright © 2009 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 23, Issue 2, pages 329–334, March/April 2009
How to Cite
Aleman, M., Nieto, J.E. and Magdesian, K.G. (2009), Malignant Hyperthermia Associated with Ryanodine Receptor 1 (C7360G) Mutation in Quarter Horses. Journal of Veterinary Internal Medicine, 23: 329–334. doi: 10.1111/j.1939-1676.2009.0274.x
- Issue published online: 3 MAR 2009
- Article first published online: 11 FEB 2009
- Submitted June 28, 2008; Revised October 11, 2008; Accepted December 18, 2008.
- Skeletal muscle
Background: Anesthetic-induced malignant hyperthermia (MH) has been documented in Quarter Horses with a single point mutation in the ryanodine receptor 1 gene (RyR1) at nucleotide C7360G, generating a R2454G amino acid substitution. However, there have been no reports of nonanesthetic manifestations of MH in horses with the C7360G mutation.
Objective: To describe clinical manifestations of Quarter Horses with the C7360G mutation.
Animals: Eleven Quarter Horses with the RyR1 C7360G mutation.
Methods: This prospective study included horses with suspected MH, undetermined etiology of sudden death, death within hours of onset of rhabdomyolysis, muscle rigidity, stiffness, intermittent sweating, and persistent increases in serum muscle enzyme activities. Whole blood in EDTA and skeletal muscle were processed for genetic and histochemical analysis. Medical records and pedigrees were collected when available.
Results: Both anesthetic- and non–anesthetic-associated myopathic manifestations of MH occurred in halter Quarter Horses with mutation of RyR1. The disease is inherited as an autosomal dominant trait. Clinical and laboratory abnormalities were similar in both forms. Rhabdomyolysis was a common finding in both groups of horses. Skeletal muscle histochemical findings were nonspecific and compatible with a noninflammatory myopathic process.
Conclusions and Clinical Importance: MH is a potentially fatal disease of Quarter Horses that could be triggered by halogenated anesthetics and other nonanesthetic factors that may include exercise, stress, breeding, illnesses, and concurrent myopathies.