A 27-year-old woman presents with acute-onset diplopia and fatigable ptosis worsening towards the end of the day. Edrophonium (Tensilon) test is positive. Anti-AChR antibodies are detected. CT thorax shows a 4 cm anterior mediastinal mass. What is the significance of the thoracic mass in this setting?

• A Lymphoma requiring biopsy before any MG treatment
• B Germ cell tumour requiring cisplatin-based chemotherapy
• C Incidental finding; treat MG with pyridostigmine alone
• D Thymoma, and thymectomy is indicated regardless of age ✓

Explanation

Thymoma is found in 10–15% of myasthenia gravis (MG) patients and is an absolute indication for thymectomy. The MGTX trial confirmed that thymectomy in non-thymomatous MG patients aged 18–65 years improved clinical outcomes and reduced immunosuppressant requirements. In thymoma-associated MG, resection is mandatory to prevent thymoma spread and also benefits MG. Pyridostigmine alone is insufficient; immunosuppression (steroids, azathioprine) is required alongside acetylcholinesterase inhibitors.

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

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Written and medically reviewed by the StethoPrep medical team.