Differential Diagnoses of Equine Myopathies
| Myopathy Type | Differential Diagnoses | 
|---|---|
| Non-exercise-associated Rhabdomyolysis | |
| Inflammatory | Influenza myositis Immune-mediated myositis | 
| Toxic | Ionophore toxicity Senna occidentalis Rayless goldenrod/white snakeroot Hypoglycin A in box elder and European sycamore trees | 
| Traumatic | Compressive anesthetic myopathy Trauma | 
| Genetic | Glycogen branching enzyme deficiency in Quarter Horse foals Polysaccharide storage myopathy types 1 and 2 Malignant hyperthermia in Quarter Horses Myosin heavy chain myopathy (Quarter Horse-related breeds) | 
| Exertional Rhabdomyolysis | |
| Focal muscle strain Overexertion, dietary imbalances, vitamins, minerals, electrolytes | |
| Polysaccharide storage myopathy types 1 and 2 Recurrent exertional rhabdomyolysis Idiopathic chronic exertional rhabdomyolysis | |
| Exertional Myopathy with Normal CK activity | |
| Polysaccharide storage myopathy type 2 Myofibrillar myopathy | |
| Muscle Atrophy | |
| Myogenic atrophy | Severe rhabdomyolysis Disuse Immune-mediated myositis (rapid atrophy) Vitamin E–responsive myopathy Homozygous polysaccharide storage myopathy type 1 Myofibrillar myopathy | 
| Neurogenic atrophy | Equine protozoal myelitis Local nerve trauma Idiopathic peripheral neuropathy Toxic peripheral neuropathies | 
| Muscle Fasciculations | |
| Pain, fear Weakness (botulism, chronic debilitation) Electrolyte abnormalities Hyperkalemic periodic paralysis Hypokalemia Otobius megnini (ear tick) infestation Stiff horse syndrome |