Neuromuscular Disorders USMLE Step 1 Practice Question
A 29-year-old woman presents with worsening diplopia and dysphagia by day's end. Vital signs show BP 118/76 mmHg, HR 82/min, RR 16/min, temp 37°C, SpO2 98% on room air. Examination reveals bilateral ptosis that increases with sustained upgaze; strength is normal. Serum anti-acetylcholine receptor antibodies are positive. Reflexes and sensation remain intact. Which of the following is the most likely diagnosis?
Answer choices
- AAmyotrophic lateral sclerosis
- BMyasthenia gravisCorrect answer
- CMultiple sclerosis
- DLambert Eaton myasthenic syndrome
- EBotulism
- FMitochondrial myopathy
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.