MuSK-Positive Myasthenia Gravis — SCE Neurology MCQ

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HardPeripheral Neuropathy & NeuromuscularMuSK-Positive Myasthenia GravisSCE Neurology

A 25-year-old woman presents with severe bulbar weakness (dysphagia, dysarthria, nasal speech) and proximal limb weakness. MuSK antibodies are positive. AChR antibodies are negative. CT chest shows no thymoma and a normal thymus. What is the most appropriate disease-modifying treatment?

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Correct answer: B — Rituximab

Explanation lettering: D = shown as C · E = shown as D · C = shown as E

MuSK-positive MG responds poorly to conventional immunosuppressants and pyridostigmine. Rituximab is recommended as an early therapeutic option in MuSK-MG per ABN 2025 guidelines and international consensus guidance. Importantly, thymectomy is NOT indicated in MuSK-MG as thymic pathology is absent. Eculizumab is only approved for AChR-positive MG. A: Thymectomy is contraindicated in MuSK-MG. C: Eculizumab targets complement (IgG1 mechanism); MuSK antibodies are IgG4 and do not fix complement. D/E: These are less effective in MuSK-MG.

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