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

This research study investigated the incidence of polysaccharide storage myopathy (PSSM), a muscle disorder, in a sample of 225 horses and ponies. The researchers found that symptoms of PSSM were present in 101 of the sampled horses, varying in degree depending on the breed.

Methodology of the Study

• The research work was carried out on muscle samples which were procured at necropsy (postmortem examination) from 225 horses and ponies that were at least one year old.
• The samples were processed and stained with hematoxylin and eosin, and with periodic acid-Schiff which is a staining method used to detect glycogen.
• The stained sections were examined for abnormal glycogen content, resistant complex polysaccharide, and chronic myopathic change—distinguished by an excessive difference in fiber size and an increase in the number of internal nuclei.

Key Findings

• The research identified 101 horses and ponies with lesions characteristic of polysaccharide storage myopathy.
• The age of the affected horses ranged from one to 30 years old, with an average age of 14.7 years, while the mean age of horses that were not affected was 12 years.
• The study discovered that the incidence of polysaccharide storage myopathy varied depending on the breed: Thoroughbreds had the lowest incidence at 27%, while draft-related horses had the highest incidence at 86%.
• Chronic myopathic changes were more severe in PSSM-affected horses than in horses that were not affected.

Conclusion

• The results of the study indicate that polysaccharide storage myopathy is a prevalent disorder in many breeds of horses and ponies.

This study provides significant insights into the occurrence and implications of polysaccharide storage myopathy across various breeds of horses and ponies, highlighting the need for further research and perhaps breed-specific care guidelines.