Neuromuscular Disorders USMLE Step 1 Practice Question
A 24-year-old man presents with recurrent episodes of transient focal weakness following minor compression injuries, including wrist drop after sleeping on his arm and foot drop after prolonged leg crossing. Vital signs: BP 118/76, HR 82, RR 16, Temp 37°C, SpO2 98%. His mother experienced similar episodes. Nerve conduction studies show focal demyelination at pressure-sensitive sites. Strength testing reveals no permanent deficits between episodes. He takes no regular medications. Which of the following is the most likely underlying problem?
Answer choices
- AAutoantibodies against acetylcholine receptors
- BDeletion affecting PMP22 leading to increased susceptibility to pressure palsiesCorrect answer
- CSMN1 gene deletion
- DToxin mediated SNARE cleavage
- EMutation causing absent dystrophin
- FPoint mutation in GJB1 causing impaired gap junction communication in peripheral nerves
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