Table 1. Clinical features of MuSK-Ab-positive and AChR-Ab-negative MG (MuSK MG) patients and MuSK-Ab-negative and AChR-Ab-negative (DSN) MG patients at the time of an initial RNS test.
| MuSK MG (n=45) | DSN MG (n=29) | p | |
|---|---|---|---|
| Sex, female | 41 (91.1) | 19 (65.5) | 0.006 |
| Age at onset, years | 37.0 (27.0–44.0) | 35.0 (26.0–46.5) | 0.982 |
| Age at time of RNS, years | 40.0 (29.5–46.0) | 37.0 (28.5–47.0) | 0.820 |
| Symptoms at time of RNS | |||
| Ocular | 34 (75.6) | 22 (75.9) | 0.976 |
| Bulbar | 41 (91.1) | 19 (65.5) | 0.006 |
| Limb | 23 (51.1) | 17 (58.6) | 0.527 |
| Neck | 22 (48.9) | 16 (55.2) | 0.598 |
| Respiratory | 14 (31.1) | 2 (6.9) | 0.014 |
| MGFA classification at time of RNS | 0.049 | ||
| Class II | 16 (35.6) | 17 (58.6) | |
| Class III | 14 (31.1) | 10 (34.5) | |
| Class IV | 5 (11.1) | 0 (0) | |
| Class V | 10 (22.2) | 2 (6.9) | |
| Severity (MGFA II+III:IV+V) | 30:15 | 27:2 | 0.008 |
| MGFA “b” classification at time of RNS | 36 (80.0) | 9 (31.0) | <0.001 |
| QMG score at the time of RNS* | |||
| Total | 11.8±4.9 | 9.7±6.8 | 0.263 |
| Ocular | 2.9±2.1 | 3.1±2.5 | 0.844 |
| Bulbar and facial | 3.6±1.9 | 1.3±2.1 | 0.001 |
| Limb | 3.4±2.8 | 4.2±3.1 | 0.361 |
| Respiratory | 0.8±1.1 | 0.4±0.7 | 0.119 |
| Neck | 1.1±1.2 | 0.8±1.0 | 0.376 |
| Immunosuppressive treatment at time of RNS | 0.333 | ||
| RNS before treatment | 26 (57.8) | 20 (69.0) | |
| RNS during treatment | 19 (42.2) | 9 (31.0) | |
| Crisis before RNS | 10 (22.2) | 2 (6.9) | 0.110 |
Data are n (%), mean±standard deviation, or median (interquartile range) values.
*QMG scores at the time of initial RNS were recorded in 22 MuSK MG and 19 DSN MG patients.
Ab: antibody, AChR: acetylcholine-receptor, DSN: double-seronegative, MG: myasthenia gravis, MGFA: Myasthenia Gravis Foundation of America, MuSK: muscle-specific tyrosine kinase, QMG: quantitative myasthenia gravis, RNS: repetitive nerve stimulation.