Immunology USMLE Step 1 Practice Question
A 48-year-old woman receives cosmetic botulinum toxin injections. Five days later, she develops diplopia, ptosis, dysphagia, and descending flaccid paralysis. Vital signs: BP 128/82 mmHg, HR 92 bpm, RR 18/min, temp 37.2°C, SpO2 98%. Electromyography shows brief, small, abundant motor action potentials. She denies recent antibiotic use. Which of the following best describes the toxin's mechanism of action?
Answer choices
- AInactivation of the 60S ribosomal subunit
- BADP ribosylation of elongation factor 2
- CPrevention of release of glycine and gamma aminobutyric acid from inhibitory interneurons
- DCleavage of SNARE proteins with inhibition of acetylcholine releaseCorrect answer
- EActivation of guanylate cyclase in intestinal epithelium
- FIrreversible inhibition of acetylcholinesterase at the neuromuscular junction
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