Immune-mediated myositis

Veterinary advice should be sought before applying any treatment or vaccine.

Immune-mediated Myositis

Immune-mediated myositis (IMM) is a rare muscle disorder where the horse's immune system attacks the skeletal muscles, resulting in rapid atrophy of the topline muscles. The disease is most frequently triggered by infection with Streptococcus spp, however 40% of IMM cases did not involve infectious agents.

Risk Factors

  • Quarter horse breed : 89
  • Under 8 years of age or 17 years of age or older : 86
  • Recently vaccinated
  • Recurring muscle atrophy : 43
  • History of respiratory infection or exposure to horses with infections : 39

Commonly Affected Breeds

Quarter Horse iconPaint Horse icon

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