Immunology USMLE Step 1 Practice Question
A 23-year-old male college student presents with a 6-month history of excessive daytime somnolence despite obtaining 7–8 hours of nocturnal sleep. He reports sudden, irresistible episodes of sleep lasting 10–30 minutes occurring multiple times daily, after which he feels briefly refreshed. He denies snoring or witnessed apneic episodes. Additionally, he describes sudden bilateral leg weakness lasting 20–60 seconds that occurs when laughing with friends or experiencing excitement. His neurologic examination is otherwise unremarkable. Brain MRI, including the hypothalamus, is normal. A lumbar puncture is performed. Which of the following CSF findings is most consistent with the patient's clinical diagnosis?
Answer choices
- AElevated 14-3-3 protein with total tau >400 pg/mL
- BDecreased hypocretin-1 (orexin-A) levels (<110 pg/mL)Correct answer
- COligoclonal bands with elevated IgG index
- DElevated neuron-specific enolase with pleocytosis
- EAnti-NMDA receptor antibodies with normal cell count
- FElevated 8-OHdG with normal protein and glucose
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