Clinical characteristics and muscle glycogen concentrations in warmblood horses with polysaccharide storage myopathy.

This research investigates the clinical characteristics and muscle glycogen concentrations in warmblood horses affected by two types of polysaccharide storage myopathy (PSSM1 and PSSM2). The study reveals rhabdomyolysis and elevated muscle glycogen concentrations in PSSM1 horses of all breeds, while most PSSM2 warmblood horses experienced stiffness and gait abnormalities with regular enzyme activities and muscle glycogen concentrations.

Methodology

• The researchers collected data from a database containing 3,615 clinical muscle biopsy submissions.
• The clinical signs and serum creatine kinase (CK) and aspartate aminotransferase (AST) activities were retrospectively analyzed for horses with PSSM1 and PSSM2.
• Lameness examinations were reviewed for 9 warmblood horses with PSSM2.
• Muscle glycogen concentrations were evaluated for horses with PSSM1, warmblood horses with PSSM2, and horses without PSSM.

Results

• Rhabdomyolysis occurred more frequently in horses with PSSM1 and non-warmblood horses with PSSM2 than in warmblood horses with PSSM2.
• Gait abnormalities were more prevalent in warmblood horses with PSSM2 than in warmblood horses with PSSM1, non-warmblood horses with PSSM2, and warmblood horses without PSSM.
• Activities of CK and AST were similar in warmblood horses with and without PSSM2.
• Muscle glycogen concentrations in warmblood and non-warmblood horses with PSSM1 were significantly higher than in warmblood horses with PSSM2.

Conclusions

• Rhabdomyolysis and increased muscle glycogen concentration were observed in horses with PSSM1 across all breeds.
• Most warmblood horses with PSSM2 displayed stiffness and gait abnormalities, yet had normal CK and AST activities and muscle glycogen concentrations.
• This indicates that different types of PSSM may result in varying clinical manifestations, and further research is needed to fully understand this complex equine disease.