Anti-MAG Neuropathy — RACP Adult Medicine MCQ

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HardNeurologyAnti-MAG NeuropathyRACP Adult Medicine

A 60-year-old man presents with progressive bilateral lower limb weakness and numbness ascending over 4 weeks. He has a history of monoclonal IgM kappa paraprotein. Anti-MAG antibodies are positive. NCS shows demyelinating neuropathy. What is the most likely diagnosis?

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Correct answer: A — Anti-MAG neuropathy

Anti-MAG (myelin-associated glycoprotein) neuropathy is a specific demyelinating neuropathy associated with IgM paraprotein. It presents with slowly progressive, predominantly sensory, distal polyneuropathy with tremor and ataxia. It is distinguished from CIDP by its distal predominance and the specific anti-MAG antibodies. Treatment is directed at the B-cell clone (rituximab is first-line). Response to IVIg and corticosteroids is generally poor, unlike CIDP.

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