Fatigable weakness, ptosis, diplopia worse in evening
ABCDE
Assess FVC/bulbar; airway support early; avoid precipitant drugs; IVIG/PLEX in crisis.
Most accurate: Anti-AChR antibodies (edrophonium/ice less specific); + CT chest for thymoma
Treat: Pyridostigmine 60 mg PO q4–6h → add steroids (daily, not alternate-day, now standard) / azathioprine; early thymectomy for AChR+ non-thymomatous gMG
Myasthenic crisis (respiratory) → IVIG or plasmapheresis + intubate; start corticosteroids a few days AFTER IVIG/PLEX initiation (immediate high-dose steroids can transiently worsen weakness)
Order set
- Anti-AChR (± MuSK)
- CT chest (thymoma)
- TFT
- FVC/NIF monitoring
Criteria
AdmitWeakness with bulbar/respiratory features
ICUCrisis: falling FVC, bulbar failure
IntubateFVC <15 mL/kg / bulbar failure / secretions
VentilateRespiratory failure in crisis
DischargeStrength recovered, FVC safe, immunotherapy + triggers reviewed
Never
- Give aminoglycosides, β-blockers, fluoroquinolones — worsen weakness
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Falling FVC
- Bulbar weakness
- Crisis triggers (infection, drugs)
Differentials
- Lambert-Eaton
- GBS
- Botulism
- Thyroid eye disease
Common mistakes
- Aminoglycosides/β-blockers
- Waiting for desaturation to support ventilation
Disposition & follow-up
Pyridostigmine + immunotherapy; crisis → ICU + IVIG/PLEX.
Discharge package
MedicationsPyridostigmine + immunotherapy; avoid precipitant drugs
Follow-upNeurology; crisis plan
Warning symptomsBreathing/swallowing difficulty, worsening weakness
💊 Treatment detail — doses & preparation
Pyridostigmineacetylcholinesterase inhibitor
Dose60 mg PO q4–6h, titrate to max 120 mg q4h
Preparation60 mg tablets (syrup available)
MonitorCholinergic excess (cramps, secretions, bradycardia); stress-dose before surgery
Prednisolonecorticosteroid
DoseMG: start low and titrate (e.g. 10–20 mg OD, increase gradually toward ~1 mg/kg if needed); in crisis delay a few days after IVIG/PLEX initiation; daily (not alternate-day) dosing now standard (ABN 2025)
Preparation5/25 mg tablets; gastro-resistant or plain with food
MonitorGlucose, BP, mood; bone protection if >3 mo (Ca²⁺/D ± bisphosphonate)
Azathioprinethiopurine immunosuppressant
Dose2–2.5 mg/kg OD (IBD, myositis, MG)
Preparation25/50 mg tablets with food
MonitorFBC + LFT weekly ×4 then q8–12 wk; TPMT before starting; avoid allopurinol combination
Rescue biologics (refractory gMG)C5 / FcRn
DoseC5 inhibitors (eculizumab/ravulizumab) or FcRn antagonists (efgartigimod, rozanolixizumab) for refractory AChR+ gMG; early rituximab esp. MuSK+
PreparationPer specialist protocol; meningococcal vaccination before C5 inhibitors
MonitorInfection, infusion reactions; neurology-led
IVIGimmunoglobulin
Dose1 g/kg/day ×2 d (ITP bleeding, GBS total 2 g/kg over 2–5 d)
Preparation50/100 mL ready bottles; start slow (30 mL/h), escalate per tolerance
MonitorHeadache/aseptic meningitis, renal function, thrombosis; live vaccines after
📖 MG International Consensus Guidance 2020 Update + ABN 2025Reviewed July 2026