A 25-year-old woman presents with ptosis and diplopia worse in the evenings, positive ice-pack test, and positive repetitive nerve stimulation (3 Hz) showing >10% decrement. Anti-AChR antibodies are elevated. CT chest shows an anterior mediastinal mass. What intervention, in addition to pyridostigmine, is most important for long-term remission?
- A Plasmapheresis as long-term maintenance therapy
- B Rituximab as first-line immunosuppression
- C Thymectomy ✓
- D Neostigmine long-acting formulation only
Correct answer: C. Thymectomy
Explanation
In myasthenia gravis with thymoma (detected on CT as an anterior mediastinal mass), thymectomy is mandatory regardless of age or severity, because of the associated thymoma which may be malignant. The MGTX trial also demonstrated that thymectomy improves outcomes in non-thymomatous AChR-positive generalized MG. Pyridostigmine treats symptoms but does not alter the disease course. Plasmapheresis and IVIG are used for myasthenic crisis (acute therapy). Long-term immunosuppression (azathioprine or mycophenolate) is often added alongside thymectomy.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.