Pathology in disorders with inflammation in muscle: comparative patterns
| Focal inflammation | Perimysial connective tissue fragmentation | Myopathic changes | Capillary pathology | Alkaline phosphatase stain | COX− muscle fibres | |
| Myositis + anti-Jo-1 antibodies | Perimysial connective tissue | Present | Perifascicular | None | Perimysial connective tissue | Infrequent |
| Dermatomyositis | Perivascular | Uncommon | Perifascicular | Yes Number ↓ | Small vessel | Perifascicular |
| Polymyositis | Endomysial Perivascular | Uncommon | Diffuse ± focal invasion of muscle fibres | None | ± Perimysial connective tissue | None, or scattered endomysial |
| Inclusion body myositis | Endomysial Perivascular | None | Diffuse: focal invasion of fibres | None | ± Small vessel | Scattered endomysial |
| Fasciitis | Perimysial connective tissue | Present | None | None | None | None |