A 25-year-old woman develops ascending paralysis, areflexia, and autonomic instability 2 weeks after Campylobacter jejuni gastroenteritis. CSF shows albuminocytologic dissociation. Nerve conduction studies (NCS) show low amplitude CMAPs with relatively preserved conduction velocities and minimal sensory involvement. Anti-GM1 antibodies are positive. What subtype of GBS does this represent?
- A AMAN (acute motor axonal neuropathy) ✓
- B AIDP (acute inflammatory demyelinating polyneuropathy)
- C AMSAN (acute motor and sensory axonal neuropathy)
- D Miller Fisher syndrome
Explanation
AMAN (Acute Motor Axonal Neuropathy) is characterized by: pure motor involvement (no/minimal sensory loss), low CMAP amplitudes with preserved conduction velocities (indicating primary axonal dysfunction rather than demyelination), anti-GM1 (and GD1a) ganglioside antibodies, and strong association with preceding Campylobacter jejuni infection. The C. jejuni lipooligosaccharide cross-reacts with GM1 gangliosides at the node of Ranvier and motor axon. AIDP shows prolonged distal latencies, slowed CVs, and conduction block. AMSAN includes sensory axon involvement. MFS is characterized by ophthalmoplegia, ataxia, and areflexia with anti-GQ1b antibodies.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.