Myasthenia gravis: muscle fatigability
A neuromuscular autoimmune disease
Dr. Antoine Mercier
Neurologist
Autoantibodies against acetylcholine receptors
Myasthenia gravis affects 1/5000. Antibodies block neuromuscular junction. Effort-induced muscle fatigability that worsens during the day. Often starts with ocular symptoms (ptosis, diplopia).
Diagnosis
Anti-AChR antibodies (85% of cases), anti-MuSK or anti-LRP4 in seronegative forms. EMG with repetitive stimulation, ice pack test. Always look for a thymoma (chest CT).
Treatments
- Pyridostigmine: symptomatic
- Corticosteroids and immunosuppressants (azathioprine, mycophenolate, rituximab)
- Thymectomy if thymoma or young generalized form
- Complement inhibitors (eculizumab, ravulizumab) and FcRn inhibitors (efgartigimod) for refractory forms
- IV immunoglobulins or plasmapheresis for myasthenic crises
Drugs to avoid
Aminoglycosides, fluoroquinolones, beta-blockers, magnesium: may worsen the disease.
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