A patient with myasthenia gravis presents with respiratory fatigue and ptosis. Which type of crisis is likely?

• A. Myasthenic crisis; differentiate from cholinergic crisis.
• B. Cholinergic crisis.
• C. Seizure crisis.
• D. Guillain-Barré crisis.

Answer: (A)

A myasthenic crisis is most likely. In myasthenia gravis, weakness worsens with use, and when the respiratory muscles—the diaphragm and intercostals—become fatigued, breathing can fail. Ptosis reflects weakness of muscles controlling eyelids and facial muscles, a common MG sign, and respiratory fatigue signals a crisis where adequate ventilation is at risk.

Differentiating from a cholinergic crisis helps clarify the cause. A cholinergic crisis results from too much acetylcholine activity (often after overdoing acetylcholinesterase inhibitors) and brings muscarinic symptoms such as increased secretions, bronchorrhea, constricted pupils, bradycardia, and sweating, sometimes with fasciculations. The Tensilon (edrophonium) test historically helps distinguish the two: improvement of weakness suggests a myasthenic crisis, while worsening indicates a cholinergic crisis. In terms of management, a myasthenic crisis requires airway support and therapies like plasmapheresis or IVIG to reduce autoantibodies, along with adjusting MG medications; a cholinergic crisis demands stopping acetylcholinesterase inhibitors and providing anticholinergic treatment (atropine) if muscarinic toxicity is present.