A 32-year-old man develops diplopia, gait ataxia, and areflexia one week after a febrile illness. Brain MRI is normal and there is no limb weakness. Which antibody, if detected, confirms the diagnosis?

• A Anti-ganglioside GQ1b ✓
• B Anti-ganglioside GD1a
• C Anti-aquaporin-4
• D Anti-P/Q-type voltage-gated calcium channel

Explanation

The triad of ophthalmoplegia, ataxia, and areflexia defines Miller Fisher syndrome, a variant of Guillain-Barre syndrome strongly linked to Campylobacter jejuni infection and characterized by IgG antibodies against ganglioside GQ1b, which is enriched in cranial nerve paranodes. Anti-GD1a associates with axonal motor GBS, aquaporin-4 with neuromyelitis optica, and P/Q-type VGCC antibodies with Lambert-Eaton myasthenic syndrome, each clinically distinct from this presentation.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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