Estimated prevalence of polysaccharide storage myopathy among overtly healthy Quarter Horses in the United States.
OBJECTIVE
To estimate the prevalence of polysaccharide storage myopathy (PSSM) among Quarter Horses in the United States and evaluate possible relationships between muscle glycogen concentration, turnout time, and exercise level.


METHODS
Cross-sectional study.


METHODS
164 overtly healthy Quarter Horses > 2 years old from 5 states.


METHODS
Horses with a history of exertional rhabdomyolysis or any other muscular disease were excluded. Muscle biopsy specimens were examined histologically for evidence of PSSM and were submitted for determination of muscle glycogen concentration. A diagnosis of PSSM was made if amylase-resistant inclusions that stained with periodic acid-Schiff stain were detected.


RESULTS
Prevalences of PSSM on the 2 farms with a history of PSSM were 20% (1/5) and 40.7% (11/27); mean prevalence for the other 4 farms was 6.1% (8/132). Sex was not significantly associated with a diagnosis of PSSM, and age was not significantly different between horses with and without PSSM. Total histologic score, serum creatine kinase activity, and muscle glycogen concentration were significantly higher in horses with PSSM than in horses without.


CONCLUSIONS
Results suggested that the prevalence of PSSM among overtly healthy Quarter Horses in the United States is likely to be between 6% and 12%.
McCue
Molly E
ME
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108, USA.
Valberg
Stephanie J
SJ
D000818:Animals; D003402:Creatine Kinase / Q000378:metabolism; D003430:Cross-Sectional Studies; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006008:Glycogen Storage Disease / Q000453:epidemiology / Q000378:metabolism / Q000662:veterinary*; D006734:Horse Diseases / Q000453:epidemiology* / Q000378:metabolism; D006736:Horses; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D015995:Prevalence; D014481:United States / Q000453:epidemiology
D006003:Glycogen; D003402:Creatine Kinase