Neuromuscular Disorders USMLE Step 1 Practice Question
A 42-year-old woman presents with progressive fatigable ptosis and nasal speech. Vital signs show BP 128/82, HR 88, RR 16, Temp 37.2°C, SpO2 98% on room air. Serum anti-acetylcholine receptor antibodies are positive. Repetitive nerve stimulation demonstrates progressively decreasing compound muscle action potentials with 15% decrement. She denies diplopia. She takes no immunosuppressive medications. Which of the following best explains her neuromuscular disorder?
Answer choices
- APresynaptic P Q type voltage gated calcium channel antibodies
- BAmyotrophic lateral sclerosis
- CPostsynaptic nicotinic acetylcholine receptor antibodiesCorrect answer
- DIncremental response with repeated stimulation
- EBotulism
- FAutoimmune destruction of muscle fiber sarcolemmal sodium channels
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