Myasthenia gravis is an autoimmune disease where antibodies block the signal between nerves and muscles, most often at the acetylcholine receptor. Weakness gets worse with use and better with rest, and it often starts in the eye muscles.
Key symptoms
- Drooping eyelids and double vision
- Weakness that worsens later in the day or with use
- Trouble chewing, swallowing or speaking clearly
- Arm and neck weakness
- Shortness of breath in severe cases
What you find on exam
- Ptosis that worsens with sustained upward gaze
- Fatigable weakness on repeated testing
- Normal reflexes and sensation
- Neck flexion strength and ability to count in one breath
Tests
- Acetylcholine receptor antibodies; MuSK antibodies if negative
- Repetitive nerve stimulation or single-fiber electromyography
- CT chest to look for a thymoma
- Forced vital capacity and negative inspiratory force if weak
Treatment basics
- Pyridostigmine for symptom relief
- Prednisone and steroid-sparing drugs such as azathioprine
- Thymectomy for thymoma or selected patients
- IV immunoglobulin or plasma exchange for myasthenic crisis
- Avoid drugs that worsen weakness, such as aminoglycosides and fluoroquinolones
Red flags
- Falling vital capacity or weak cough
- Trouble swallowing with choking
- Rapidly worsening weakness after a new medicine or infection
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.