## Key Pathophysiological Features of GBS **Key Point:** Autonomic dysfunction in GBS is NOT uncommon — it is a well-recognized and clinically significant complication that can be life-threatening. ### Why Option 2 (Autonomic Dysfunction) is WRONG Autonomic involvement occurs in **50–70% of GBS patients** and includes: - **Cardiovascular:** Arrhythmias, labile blood pressure, orthostatic hypotension, sudden cardiac death - **Gastrointestinal:** Ileus, constipation - **Urinary:** Urinary retention - **Pupillary:** Pupil abnormalities, accommodation paralysis **Clinical Pearl:** Sudden cardiac death from autonomic dysrhythmia is a recognized cause of mortality in GBS, particularly in patients requiring ICU care. Continuous cardiac monitoring is standard in moderate-to-severe cases. ### Why the Other Options are CORRECT | Feature | Details | |---------|----------| | **Demyelination (Option 0)** | Classic acute inflammatory demyelinating polyradiculoneuropathy (AIDP) accounts for ~90% of GBS cases in developed countries; axonal variants (AMAN, AMSAN) are more common in Asia | | **Respiratory involvement (Option 1)** | ~25–30% of GBS patients require mechanical ventilation; this is the leading cause of hospitalization and mortality in GBS | | **Anti-ganglioside antibodies (Option 3)** | Anti-GQ1b associated with Miller Fisher syndrome (ophthalmoplegia, ataxia, areflexia); anti-GM1 with axonal variants; anti-GD1a with AMAN | **High-Yield:** The question tests whether students confuse GBS as a purely motor/sensory disorder and overlook the autonomic complications — a common exam trap. [cite:Harrison 21e Ch 446]
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