| Domain | Score | |||
|---|---|---|---|---|
| 0 | 1 | 2 | 3 | |
|
Inflammation Inflammatory cell infiltration (endomysium: score×2) |
None (< 10 cells at 20× high power field) |
1 cluster (≥ 10 cells at 20× high power field) |
2 clusters | ≥ 3 clusters |
|
Vascular Vasculitis |
none | 1 vessel | 2 vessels | ≥ 3 vessels |
| Muscle | ||||
| Atrophy (perifascicular atrophy: score ×2) |
≤ 5% of total area | 6–25% | 26–50% | > 50% |
| Degenerative fibers | ≤ 5% of total area | 6–25% | 26–50% | > 50% |
| Internal nuclei | Absent (≤ 3/100 fibers) |
Present (> 3/100 fibers) |
||
| Invaded non-necrotic fibers |
none | 1 fascicle | 2 fascicles | ≥ 3 fascicles |
|
Connective tissue Endomysial fibrosis |
none | thin with angular fibers | moderate thick with blunt fibers | markedly thick with round fibers |