Muscle biopsy features, treatments, and duration of disease in anti-Jo1–positive patients diagnosed with DM and PM.
| DM, n (%) | PM, n (%) | p | |
|---|---|---|---|
| Perivascular inflammation | 9 (69.2) | 6 (85.7) | 0.6 |
| Perifascicular atrophy | 8 (61.5) | 4 (57.1) | 1 |
| Primary inflammation | 4 (30.8) | 4 (57.1) | 0.4 |
| Mitochondrial dysfunction* | 2 (25.0) | 2 (16.7) | 1 |
| Necrotizing myopathy | 2 (15.4) | 0 (0.0) | 0.5 |
| Immunosuppression prior to biopsy | 8 (61.5) | 3 (42.9) | 0.6 |
| Taking immunosuppression during biopsy | 6 (54.4) | 3 (42.9) | 1 |
| Corticosteroids during biopsy | 4 (30.8) | 2 (28.6) | 1 |
| Days from the onset of symptoms to the biopsy, median (Q1–Q3) | 725 (531–874) | 374 (37–435) | 0.1 |
↵* Because not all biopsies were stained with cytochrome oxidase, mitochondrial dysfunction could not be assessed in all cases. Fisher’s exact test and Wilcoxon rank-sum test p values are shown for the categorical and quantitative variables, respectively. DM: dermatomyositis; PM: polymyositis.