Clinical characteristics, diagnostic findings, management, and outcomes of ICI-related MG in patients with pre-existing MG (n = 13) and those with new onset disease (n = 52)a
| Variable | New Onset (n = 52); n (%) | Pre-existing MG (n = 13); n (%) | p value |
|---|---|---|---|
| Median time from ICI initiation to onset of MG symptoms (weeks) | 0.27 | ||
| 4 | 4.7 | ||
| MGFA classification | 0.161 | ||
| I | 7 (14) | 1 (8) | |
| II | 14 (27) | 0 | |
| III | 6 (12) | 2 (15) | |
| IV | 2 (4) | 2 (15) | |
| V | 23 (44) | 6 (46) | |
| Clinical presentation | |||
| Ptosis | 43 (83) | 6 (46) | 0.01 |
| Dyspnea | 32 (62) | 8 (62) | 1 |
| Limb weakness | 30 (58) | 6 (46) | 0.54 |
| Dysphagia | 24 (46) | 7 (54) | 0.76 |
| Diplopia | 22 (42) | 5 (39) | 0.8 |
| Neck weakness | 20 (39) | 2 (15) | 0.19 |
| Myalgias | 13 (25) | 0 | 0.06 |
| Blurry vision | 7 (14) | 0 | 0.33 |
| Dysarthria | 6 (12) | 2 (15) | 0.65 |
| Generalized weakness | 6 (12) | 0 | 0.34 |
| Dysphonia | 6 (12) | 1 (8) | 1 |
| Facial weakness | 5 (10) | 3 (23) | 0.19 |
| Nasal speech/weakness of the palatal muscles | 5 (10) | 1 (8) | 1 |
| Incontinence | 2 (4) | 0 | 1 |
| Diagnostic tools | |||
| Auto antibody panel positive titers | |||
| Anti-AChR | 32/50 (64) | 5/6 (83) | 0.65 |
| Anti-Striated muscle | 12/18 (67) | 0/0 | N/A |
| Muscle enzymes elevation | |||
| CPK | 37/44 (84) | 4/5 (80) | 1 |
| Troponin | 12/13 (92) | 1/1 (100) | 1 |
| Edrophonium test positive | 5/5 (100) | 0 | N/A |
| Ice pack test positive | 2/4 (50) | 0 | N/A |
| Electrodiagnostic studies (skeletal muscle EMG, RNS, NCS) | |||
| MG | 14/34b (41) | 2/3 (67) | 0.56 |
| Myopathy | 6/34c (18) | 0/3 | 0.58 |
| MG and myopathy | 6/34c (18) | 0/3 | 0.33 |
| Polyneuropathy | 2/34 (6) | 1/3 (33) | 0.23 |
| No pathologic findings | 6/34 (18) | 0/3 | 0.58 |
| Treatment of MG | |||
| Corticosteroids | 48 (92) | 11/11d (100) | 1 |
| Acetylcholinesterase inhibitors | 25 (48) | 7/11d (64) | 0.35 |
| IVIG | 25 (48) | 5/11d (46) | 0.87 |
| Plasmapheresis | 22 (42) | 6/11d (55) | 0.52 |
| Other IST (MMF, rituximab, infliximab or tacrolimus) | 7 (13) | 3/11d (27) | 0.36 |
| IA | 3 (6) | 0/11d | 1 |
| ICI holding/discontinuation | 51 (98) | 10/11d (91) | 0.32 |
| MG outcome | |||
| Complete resolution | 8/51 (16) | 4/11d (36)e | 0.2 |
| Improvement | 30/51e (59) | 4/11d (36) | 0.2 |
| Deterioration | 13/51e (26) | 3/11d (27) | 1 |
| Death | 21 (40) | 3 (23) | 0.34 |
| MG complications | 13 (25) | 2 (15) | 0.72 |
| Cancer progression | 4 (8) | 0 | 0.58 |
| Other comorbidities | 2 (4) | 1 (8) | 0.5 |
| Unspecified | 2 (4) | 0 | 1 |
aAbbreviations: MG myasthenia gravis, ICI immune checkpoint inhibitor, MGFA Myasthenia Gravis Foundation of America, Anti-AChR Anti-Acetylcholine receptor, CPK creatine phosphokinase, EMG electromyography, RNS repetitive nerve stimulation, NCS nerve conduction study, IVIG intravenous immunoglobulin, IST immunosuppressive therapy, MMF mycophenolic acid, IA immunoadsorption. Numbers are rounded to the nearest whole number
bThree patients also had findings suggestive of polyneuropathy
cTwo patients also had findings suggestive of polyneuropathy
dTwo patients with pre-existing MG did not develop a flare of their disease after ICI initiation and were excluded from the analysis
eData were not reported for one patient