Epidemiologic characteristics and management of polysaccharide storage myopathy in Quarter Horses.
OBJECTIVE
To characterize onset and clinical signs of polysaccharide storage myopathy (PSSM) in a well-defined population of affected Quarter Horses, identify risk factors for PSSM, determine compliance of owners to dietary and exercise recommendations, and evaluate the efficacy of dietary and exercise recommendations.


METHODS
40 Quarter Horses with PSSM and 37 unaffected control horses.


METHODS
Owners of horses with PSSM completed a retrospective questionnaire concerning their horse's condition.


RESULTS
Between horses with PSSM and control horses, no significant differences were found in sex distribution (21 vs 15 females and 16 vs 22 males, respectively), temperament, muscle build, diet, or amount of turnout. In horses with PSSM, signs of muscle stiffness, muscle fasciculations, sweating, exercise intolerance, weakness, muscle wasting, reluctance to move, colic, abnormal gait, recumbency, lameness, and swollen muscles began between the age of 1 day and 14 years (mean age, 4.9 +/- 3.5 years). Five horses with PSSM developed acute muscle atrophy. Sixty-three percent (25/40) of owners fed the recommended diet, 55% (22/40) provided regular exercise, and 40% (16/40) followed both dietary and exercise recommendations. Owners of affected horses for which a decrease in severity or frequency of PSSM was not found did not follow the exercise, dietary, or both recommendations. All horses for which both dietary and exercise recommendations were followed had improvement in signs of PSSM.


CONCLUSIONS
n addition to exertional rhabdomyolysis, signs of PSSM include acute muscle atrophy and gait abnormalities. It appears that PSSM can be managed by following dietary recommendations combined with gradual increases in daily exercise.
Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108, USA.
Anna M
AM
Firshman
Stephanie J
SJ
Valberg
Jeffrey B
JB
Bender
Carrie J
CJ
Finno
D000818:Animals; D005260:Female; D006008:Glycogen Storage Disease / Q000453:epidemiology / Q000473:pathology / Q000628:therapy / Q000662:veterinary*; D006734:Horse Diseases / Q000453:epidemiology* / Q000473:pathology / Q000628:therapy; D006736:Horses; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology*; D009135:Muscular Diseases / Q000453:epidemiology / Q000473:pathology / Q000628:therapy / Q000662:veterinary*; D010805:Physical Conditioning, Animal