A 35-year-old woman with myasthenia gravis has positive anti-AChR antibodies and CT chest reveals a 4 cm anterior mediastinal mass. The MOST appropriate next steps are:

• A Pyridostigmine optimisation only; thymoma is benign in MG
• B Radiotherapy to the mediastinal mass followed by azathioprine
• C Rituximab for refractory MG; surgery only if mass grows
• D Thymectomy is indicated for both the thymoma and to improve MG; preceded by immunosuppressive optimisation ✓

Explanation

In MG with thymoma, surgical thymectomy is mandatory for oncological reasons (thymomas have malignant potential — WHO classification A through C) and also benefits MG itself. Preoperative optimisation with pyridostigmine and immunosuppressants (prednisolone ± azathioprine) is essential to achieve stable MG before surgery and prevent postoperative myasthenic crisis. The MGTX trial confirmed thymectomy benefit in non-thymomatous generalised AChR-positive MG as well. Rituximab is reserved for anti-MuSK-positive or refractory MG.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.