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MG – Azathioprine Lag Period — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularMG – Azathioprine Lag PeriodSCE Neurology

A 35-year-old woman with AChR-positive generalised myasthenia gravis on prednisolone and azathioprine has a relapse with worsening proximal weakness and dysphagia. Her FVC is declining. She is started on IVIg. After IVIg, her symptoms improve but relapse within 4 weeks. Her azathioprine has been at full dose for only 8 weeks. What is the most important consideration?

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Correct answer: D — Give another course of IVIg as a bridge while waiting for azathioprine to reach full efficacy

Azathioprine typically takes 6–18 months to reach full immunosuppressive efficacy. At only 8 weeks, it is too early to judge its effectiveness. IVIg (or PLEX) can be used as a 'bridge' to cover the lag period until azathioprine takes effect. Repeated courses every 4–6 weeks may be necessary. A: 8 weeks is insufficient to assess azathioprine efficacy. C: Rituximab is reserved for refractory AChR-positive MG or MuSK MG. D: Thymectomy should be considered electively but is not urgent management for an acute relapse. E: Adding ciclosporin may be considered if azathioprine fails after adequate trial.

Reference: ABN MG Guidelines (2025); MGFA International Consensus Guidance (2020)