A 35-year-old woman presents with bilateral ptosis worsening toward evening, diplopia, and fatigable proximal limb weakness. Repetitive nerve stimulation at 3 Hz shows 15% decremental response. Serum anti-AChR antibodies are positive. CT chest shows a 4 cm anterior mediastinal mass. The most appropriate definitive management of this mediastinal mass is:
- A Thymectomy (extended transsternal) ✓
- B Radiation therapy to the mediastinum
- C Observation and pyridostigmine alone
- D Chemotherapy with cisplatin-based regimen
Explanation
Thymoma is present in approximately 10–15% of MG patients, and MG occurs in ~30–40% of thymoma patients. When thymoma is identified in MG, surgical resection (extended transsternal thymectomy) is mandatory regardless of age or severity because thymomas are potentially invasive tumors. The MGTX randomized trial confirmed that thymectomy (even in non-thymomatous MG) improved clinical outcomes and reduced immunosuppressive requirements. Radiation and chemotherapy are for unresectable or invasive thymoma. Pyridostigmine alone is symptomatic therapy, not definitive for thymoma.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.