A 35-year-old woman with myasthenia gravis generalised (MGFA class III) has anti-AChR antibody titre 42 nmol/L. CT chest shows thymoma. After thymectomy, she still has incomplete response on pyridostigmine. According to MGTX trial and MGFA guidelines, the next immunosuppressive drug of choice is:
- A Azathioprine ✓
- B Methotrexate
- C Eculizumab
- D Plasma exchange alone
Explanation
Azathioprine is the established first-line steroid-sparing immunosuppressive for generalised myasthenia gravis after failure of or dependence on corticosteroids. The MGTX trial confirmed the benefit of thymectomy in non-thymomatous MG; after thymectomy, persistent symptoms require immunosuppression, and azathioprine 2–3 mg/kg/day is guideline-recommended as first-line. Mycophenolate mofetil is a common alternative. Eculizumab (anti-C5 complement inhibitor) is approved for refractory generalised AChR-positive MG. Methotrexate has limited evidence in MG. Plasma exchange provides short-term benefit for myasthenic crisis but is not maintenance therapy.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.