Myasthenia gravis
auto-antibodies to AChR; anti-Musk (lol) - muscle-specific tyosine kinase
| Headline | |
|---|---|
| Etiology | auto-antibodies against AChRs. |
| Epidemiology | F>M, onset peaks at 30y, 60y for women; 70y for men. MuSK-directed MG more common in Black women |
| Clinical presentation | ptosis, dysphagia, dysarthria, facial paresis, proximal limb weakness. Ddx: Lambert-Eaton (associated with small cell lung cancer) |
| Pathogenesis | Type 2 hypersensitivity |
| Diagnostic investigations | Auto-abs against AChRs or MuSK; serial spirometry; repetitive stimulation (excludes Lambert-Eaton); single-fibre EMG. MG vs LEMS: edrophonium testing - MG confirmed if sudden but temporary improvement. Rarely used now (s/e: ↓ HR, ↓ BP - reverse with atropine) |
| Management | Pyridostigmine with frequent s/s (s/e: muscarinic – mitigate with glycopyrronium). ➥ Corticosteroids (start at 15-20mg) or AZT/MYC etc. ➥ IvIG ⚠ ↓WCC/plt, MI, stroke ➥ serial ~FVCs on initial assessment ➥ Thymectomy ➥ Exacerbations with pregnancy, infection, surgery |
drugs to avoid
- aminoglycosides, macrolides, fluoquinolones
- beta blockers
- immune checkpoint inhibitors
- statins
- iodinated contrast
- live attenuated vaccines
- procainamide
- HCQ
- D-penicillamine
- Desferrioxamine