A 52-year-old woman presents with ptosis, diplopia, and proximal limb weakness that worsens during the day. Repetitive nerve stimulation at 3 Hz shows a 20% decremental response. Anti-AChR antibodies are positive. CT chest reveals a thymoma. Which treatment is indicated as an early-stage disease-modifying measure alongside pyridostigmine?
- A Thymectomy in AChR-antibody positive MG with thymoma is mandatory ✓
- B Azathioprine immunosuppression only, defer thymectomy
- C Plasmapheresis as maintenance therapy
- D Eculizumab monotherapy replaces all other treatment
Correct answer: A. Thymectomy in AChR-antibody positive MG with thymoma is mandatory
Explanation
In myasthenia gravis associated with thymoma, thymectomy is mandatory regardless of disease severity because thymoma carries malignant potential. The MGTX trial demonstrated that thymectomy in non-thymomatous generalised AChR-Ab+ MG also improves outcomes. Azathioprine is used as a steroid-sparing agent but does not remove the thymoma. Plasmapheresis is used for myasthenic crisis or pre-operative preparation, not chronic maintenance.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.