TABLE 3.
Clinicopathologic features of 249 patients with IBM according to anti‐NT5C1A antibody status
| Anti‐NT5C1A positive | Anti‐NT5C1A negative | P 1 | |
|---|---|---|---|
| Number of patients | 159 (64) | 90 (36) | |
| Sex (M:F) | 92:67 | 54:36 | 0.80 |
| Age at onset, mean (SD), years | 58.8 (8.3) | 60.3 (9.3) | 0.21 |
| Onset to biopsy, mean (SD), years | 5.2 (4.6) | 5.6 (5.1) | 0.60 |
| Maximum CK level, median, IU/L | 425 | 308 | 0.11 |
| Dysphagia | 82/158 (52) | 40/85 (47) | 0.50 |
| Knee extension weakness (≥ hip flexion weakness) | 121/159 (76) | 69/90 (77) | >0.99 |
| Finger flexion weakness (> shoulder abduction weakness) | 145/159 (91) | 68/90 (76) | <0.01 |
| Muscle biopsy findings | |||
| Rimmed vacuoles | 93/159 (58) | 63/90 (70) | 0.08 |
| Protein accumulation | 71/95 (75) | 53/64 (83) | 0.25 |
| Endomysial inflammatory infiltrate | 147/155 (95) | 79/89 (89) | 0.12 |
| Focal invasion of non‐necrotic fibers | 84/117 (72) | 43/71 (61) | 0.15 |
| MHC‐class1 upregulation | 78/85 (92) | 51/61 (84) | 0.19 |
| Qualitative analysis of COX‐negative fibers 2 | 86/122 (70) | 52/76 (68) | 0.75 |
| COX‐negative fibers, mean (SD), % 2 | 3.2 (3.9) | 2.1 (2.3) | 0.04 |
| SDH‐positive fibers, mean (SD), % 2 | 2.2 (2.9) | 2.0 (2.8) | 0.69 |
CK, creatine kinase; COX, cytochrome oxidase; IBM, inclusion body myositis; SDH, succinate dehydrogenase. Values are no. (%) unless otherwise indicated.
1
Bonferroni corrected significance thresholds for clinical features and biopsy findings were 0.003 and 0.007, respectively. The P‐values less than 0.05 are marked in bold.
2
The percentages of COX‐negative and SDH‐positive muscle fibers were determined by photographing a random field with a 10x objective and counting 200 fibers. We set cutoff value as 1.0% for qualitative analysis of COX‐negative fibers.