A 40-year-old woman with myasthenia gravis (acetylcholine receptor antibody positive, thymoma present) is admitted with worsening weakness, ptosis, and dysarthria. She is on pyridostigmine 60 mg 5 times daily. FVC is 1.8 L (30% predicted). What is the immediate next step?
- A Increase pyridostigmine dose
- B Plasmapheresis or IVIG + elective intubation preparation ✓
- C IV methylprednisolone pulse therapy
- D Edrophonium (Tensilon) test to confirm myasthenic crisis vs. cholinergic crisis
Explanation
Myasthenic crisis is defined by respiratory failure requiring ventilatory support (FVC <1 L or <20 mL/kg is the threshold for intubation; <2 L warrants ICU monitoring). Immediate treatment is plasmapheresis (PLEX) or IVIG to rapidly remove antibodies — both are equally effective per Cochrane data, with PLEX acting slightly faster. Pyridostigmine should be withheld during crisis to reduce secretions. High-dose steroids can initially worsen MG and are not given emergently in crisis. Edrophonium test is rarely used in modern practice and risks cholinergic crisis in those already on high pyridostigmine.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.