Exertional rhabdomyolysis in quarter horses and thoroughbreds: one syndrome, multiple aetiologies.
Abstract: The purpose of this study was to determine if chronic exertional rhabdomyolysis (ER) in Quarter Horses and Thoroughbreds represents one or several distinct myopathies. Eighteen Quarter Horses and 18 Thoroughbreds with ER were selected from cases presented to the Veterinary Hospital on the basis of a history of ER, assessment of muscle histopathology, and serum CK activity before and 4 h post exercise. In addition, 2 of 3 of the following parameters were evaluated: muscle glycogen concentrations, thyroid hormones (T3, T4), fractional excretion (FE) of sodium, potassium and chloride. The CK response to training, the metabolic response to a near maximal standardised exercise test (SET), blood glucose concentrations after an i.v. glucose challenge and a skeletal muscle in vitro caffeine contracture test were performed on 5 of the Quarter Horses, selected because of polysaccharide storage myopathy (PSSM), and 5 of the Thoroughbreds. Serum T3 and T4 were all within normal limits. Low FE of sodium and potassium were seen in < 20% of Quarter Horses and Thoroughbreds. Four hours post exercise, CK was increased in 77% of Quarter Horses and 72% of Thoroughbreds with ER. Muscle glycogen concentrations in Quarter Horses with ER were significantly higher than in normal Quarter Horses and Thoroughbreds with ER. No Thoroughbreds, but 15/18 Quarter Horses with ER had abnormal polysaccharide accumulation in muscle biopsies consistent with a diagnosis of PSSM. PSSM Quarter Horses had higher CK activity during training than Thoroughbreds and higher glycogen utilisation with the SET. PSSM Quarter Horses also had significantly enhanced glucose clearance compared to normal Quarter Horses and Thoroughbreds with ER. Thoroughbreds with ER had significantly lower thresholds for caffeine-induced contracture than normal horses and PSSM Quarter Horses. It was concluded that there are multiple causes for exertional rhabdomyolysis. In Quarter Horses, rhabdomyolysis is commonly due to a glycogen storage disorder, PSSM, and is readily expressed in untrained horses. In Thoroughbreds, ER is commonly due to an underlying abnormality of muscle contraction. Rhabdomyolysis in Thoroughbreds, however, is only expressed intermittently when key stressors are present.
Publication Date: 2000-02-05 PubMed ID: 10659313DOI: 10.1111/j.2042-3306.1999.tb05279.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates whether chronic exertional rhabdomyolysis (ER), a muscle condition, in quarter horses and thoroughbreds is the same or different, finding that there are multiple causes for the disorder, differing between horse species.
Methods of the Study
- The researchers selected 18 quarter horses and 18 thoroughbreds with ER, based on their history of the condition, their muscle histopathology, and serum CK activity, both before and after exercise.
- Other parameters evaluated included muscle glycogen levels, thyroid hormones (T3, T4), and the excretion rates of sodium, potassium, and chloride.
- An in-vitro skeletal muscle caffeine contracture test, glucose challenge following exercise, and CK response to training, were performed on a subset of the selected horses—five from each breed.
Results of the Study
- Results revealed that CK activity increased 4 hours post exercise in 77% of the quarter horses and 72% of the thoroughbreds with ER.
- The muscle glycogen concentrations in quarter horses with ER were significantly higher than in healthy quarter horses and thoroughbreds with ER.
- Abnormal accumulation of polysaccharide, consistent with a diagnosis of Polysaccharide Storage Myopathy (PSSM), was found in 15 out of 18 quarter horses but none of the thoroughbreds.
- The PSSM quarter horses had higher CK activity during training, higher glycogen utilisation in exercise tests, and markedly improved glucose clearance compared to normal quarter horses and thoroughbreds with ER.
- Thoroughbreds with ER had significantly lower thresholds for caffeine-induced muscle contraction than either healthy horses or PSSM quarter horses.
Conclusions of the Study
- The researchers concluded that exertional rhabdomyolysis (ER) has multiple causes.
- In quarter horses, ER is commonly due to a glycogen storage disorder called PSSM, which is readily expressed in untrained horses.
- Whereas, in thoroughbreds, it is frequently due to an abnormality of muscle contraction which only comes to light during certain stress factors.
Cite This Article
APA
Valberg SJ, Mickelson JR, Gallant EM, MacLeay JM, Lentz L, de la Corte F.
(2000).
Exertional rhabdomyolysis in quarter horses and thoroughbreds: one syndrome, multiple aetiologies.
Equine Vet J Suppl(30), 533-538.
https://doi.org/10.1111/j.2042-3306.1999.tb05279.x Publication
Researcher Affiliations
- Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
MeSH Terms
- Animals
- Biopsy / veterinary
- Blood Glucose / metabolism
- Caffeine / pharmacology
- Creatine Kinase / blood
- Exercise Test / veterinary
- Glucose Tolerance Test / veterinary
- Horse Diseases / etiology
- Horse Diseases / pathology
- Horses
- Muscle Contraction / drug effects
- Muscles / pathology
- Physical Conditioning, Animal / adverse effects
- Rhabdomyolysis / veterinary
Citations
This article has been cited 11 times.- Hansen S, Hopster-Iversen C, Berg L, Fjeldborg J, Massey C, Piercy RJ, Carstensen H. Chronic idiopathic myopathy in Icelandic horses: A case series. Equine Vet J 2025 Sep;57(5):1341-1346.
- Durward-Akhurst SA, Valberg SJ. Myosin Heavy Chain Myopathy and Immune-Mediated Muscle Disorders. Vet Clin North Am Equine Pract 2025 Apr;41(1):61-75.
- Lindsay-McGee V, Massey C, Li YT, Clark EL, Psifidi A, Piercy RJ. Characterisation of phenotypic patterns in equine exercise-associated myopathies. Equine Vet J 2025 Mar;57(2):347-361.
- Schumacher A, Gehlen H. Health of Polo Horses. Animals (Basel) 2024 Jun 8;14(12).
- Santifort KM, Plonek M, Mandigers PJJ. Clinical Diagnosis of Rhabdomyolysis without Myoglobinuria or Electromyographic Abnormalities in a Dog. Animals (Basel) 2023 May 25;13(11).
- Hebert JF, Burfeind KG, Malinoski D, Hutchens MP. Molecular Mechanisms of Rhabdomyolysis-Induced Kidney Injury: From Bench to Bedside. Kidney Int Rep 2023 Jan;8(1):17-29.
- Valberg SJ, Velez-Irizarry D, Williams ZJ, Henry ML, Iglewski H, Herrick K, Fenger C. Enriched Pathways of Calcium Regulation, Cellular/Oxidative Stress, Inflammation, and Cell Proliferation Characterize Gluteal Muscle of Standardbred Horses between Episodes of Recurrent Exertional Rhabdomyolysis. Genes (Basel) 2022 Oct 14;13(10).
- Buckley P, Buckley DJ, Freire R, Hughes KJ. Pre-race and race management impacts serum muscle enzyme activity in Australian endurance horses. Equine Vet J 2022 Sep;54(5):895-904.
- Norton EM, Mickelson JR, Binns MM, Blott SC, Caputo P, Isgren CM, McCoy AM, Moore A, Piercy RJ, Swinburne JE, Vaudin M, McCue ME. Heritability of Recurrent Exertional Rhabdomyolysis in Standardbred and Thoroughbred Racehorses Derived From SNP Genotyping Data. J Hered 2016 Nov;107(6):537-43.
- Fritz KL, McCue ME, Valberg SJ, Rendahl AK, Mickelson JR. Genetic mapping of recurrent exertional rhabdomyolysis in a population of North American Thoroughbreds. Anim Genet 2012 Dec;43(6):730-8.
- Isgren CM, Upjohn MM, Fernandez-Fuente M, Massey C, Pollott G, Verheyen KL, Piercy RJ. Epidemiology of exertional rhabdomyolysis susceptibility in standardbred horses reveals associated risk factors and underlying enhanced performance. PLoS One 2010 Jul 14;5(7):e11594.
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