Canine Polymyositis

• DOES NOT include Masticatory Muscle Myositis
• Rare
• Clinical signs:
  • Muscle pain
  • Fever
  • Weakness, particularly in hind limbs
• Grossly:
  • Inflammation is accompanied by muscle necrosis and regeneration
• Histologically:
  • Inflammatory foci with lymphocytes, plasma cells and occasionally eosinophils
• Possibly immunological cause
• Single biopsy may not be enough to make the diagnosis as it tends to be multifocal and disseminated
• Lesions similar to some infectious causes (such as Toxoplasma gondii)