Anti-MAG Neuropathy Treatment — RACP Adult Medicine MCQ

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HardNeurologyAnti-MAG Neuropathy TreatmentRACP Adult Medicine

A 50-year-old man presents with a 3-month history of progressive bilateral lower limb weakness and sensory ataxia. He has a monoclonal IgM paraprotein. Anti-MAG antibodies are strongly positive. NCS shows distal-predominant demyelinating neuropathy. What is the first-line treatment?

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Correct answer: D — Corticosteroids

Anti-MAG neuropathy is an IgM paraprotein-associated demyelinating neuropathy. Unlike CIDP (which responds well to IVIg and corticosteroids), anti-MAG neuropathy responds poorly to these treatments. Rituximab (targeting the B-cell clone producing the IgM anti-MAG antibody) is the first-line treatment, with response rates of 30–50% (RIMAG trial and meta-analyses). Response is slow (months). Plasma exchange may provide temporary improvement. Treatment aims to stabilise rather than reverse the neuropathy, as recovery of demyelinated peripheral nerves is slow and often incomplete.

Reference: eTG – 2025 – Neurology; EAN/PNS – 2021 – Paraproteinaemic Neuropathy