Equine Muscle Disorders and Genetic Mechanisms

Equine muscle disorders encompass a range of hereditary and acquired conditions that compromise locomotory performance, welfare and longevity. Among these, polysaccharide storage myopathy (PSSM) arises from gain-of-function mutations in the glycogen synthase gene (GYS1), leading to excessive intramyofibrillar accumulation of non-crystalline glycogen and resultant muscle stiffness and rhabdomyolysis. Recurrent exertional rhabdomyolysis (RER) typically affects Thoroughbreds and Standardbreds, and is characterised by exercise-induced myofibre damage linked to aberrant calcium handling at the level of the sarcoplasmic reticulum. Myofibrillar myopathy (MFM), observed in Arabian horses, features progressive myofibrillar disarray, desmin aggregation and oxidative imbalance in cysteine metabolic pathways. Immune-mediated myositis (IMM), notably in Quarter Horses, involves lymphocytic infiltration of type 2X fibres and is associated with a missense variant in a myosin heavy chain gene. Recent omics approaches—integrating transcriptome and proteome profiling—have delineated interconnected pathways of energy metabolism, calcium regulation, redox homeostasis and inflammatory signalling. Advances in genetic screening, non-invasive electromyography and computational phenotyping are refining diagnostic precision and uncovering potential therapeutic targets, with implications for selective breeding and clinical management on a global scale.

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Equine Muscle Disorders and Genetic Mechanisms publication trend

The graph below shows the total number of articles in equine muscle disorders and genetic mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Polysaccharide storage myopathy (PSSM): A glycogen storage disorder caused by GYS1 mutations, leading to intramuscular accumulation of abnormal glycogen.

Recurrent exertional rhabdomyolysis (RER): An exercise‐induced muscle damage syndrome linked to dysregulated calcium release from the sarcoplasmic reticulum.

Exercise‐associated myopathy syndrome (EAMS): A phenotype of exercise-related muscle pain and motor reluctance distinguished by computational clustering of clinical signs.

Surface electromyography (sEMG): A non-invasive technique for recording electrical activity of muscle fibres during movement.

Missense mutation: A single nucleotide change resulting in an amino acid substitution that may alter protein function.

Transcriptome: The complete set of RNA transcripts expressed in a tissue under specific conditions.

Proteome: The entire complement of proteins present in a cell or tissue at a given time.

References

1. A missense mutation in MYH1 is associated with susceptibility to immune-mediated myositis in Quarter Horses. Skeletal Muscle (2018).
2. Proteome and transcriptome profiling of equine myofibrillar myopathy identifies diminished peroxiredoxin 6 and altered cysteine metabolic pathways. Physiological Genomics (2018).
3. Pathways of calcium regulation, electron transport, and mitochondrial protein translation are molecular signatures of susceptibility to recurrent exertional rhabdomyolysis in Thoroughbred racehorses. PLOS ONE (2021).
4. Characterisation of phenotypic patterns in equine exercise‐associated myopathies. Equine Veterinary Journal (2024).
5. Comparison of gluteus medius muscle activity in Haflinger and Noriker horses with polysaccharide storage myopathy. Journal of Animal Physiology and Animal Nutrition (2021).