Incidence of polysaccharide storage myopathy: necropsy study of 225 horses.

Department of Biomedical Sciences, College of Veterinary Medicine, Magruder 142, Oregon State University, Corvallis, OR 97331, USA.
Veterinary Pathology (Impact Factor: 2.04). 12/2005; 42(6):823-7. DOI: 10.1354/vp.42-6-823
Source: PubMed

ABSTRACT Muscle samples were obtained at necropsy from 225 horses and ponies 1 year of age or older. Samples were processed in routine manner and were stained with hematoxylin and eosin and with periodic acid-Schiff for glycogen. Sections were examined for abnormal glycogen content and amylase-resistant complex polysaccharide and for chronic myopathic change (excessive fiber size variation, increase in number of internal nuclei). A total of 101 horses and ponies with lesions of polysaccharide storage myopathy were identified. Age of affected horses ranged from one to 30 years, with a mean of 14.7 years. Mean age of nonaffected horses was 12 years. Incidence of polysaccharide storage myopathy varied depending on breed; Thoroughbreds had the lowest (27%) and draft-related horses had the highest (86%) incidence. Chronic myopathic changes were more severe in polysaccharide storage myopathy-affected horses than in nonaffected horses. Results of this study indicate that polysaccharide storage myopathy is a common disorder of many breeds of horses and ponies.

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