A 19-year-old male college student is brought to the clinic by his parents due to worsening academic performance and concerns about his health. Over the past year, he has found it increasingly difficult to stay awake during lectures and while studying. He describes an overwhelming “sleep attack” that forces him to nap, after which he feels refreshed for an hour or two. His grades have declined significantly. He also reports several episodes of suddenly feeling his “knees give out” when laughing heartily at jokes with his friends. These episodes of weakness last less than a minute, and he has never lost consciousness. He also mentions experiencing very vivid, often frightening, dream-like images as he is falling asleep. On two occasions, he woke up and found himself unable to move or speak for a few seconds, which was terrifying. His parents report that he often kicks and mumbles in his sleep. His past medical history is unremarkable except for a 20-pound weight gain over the last year. He denies use of alcohol, tobacco, or illicit drugs.

Initial laboratory studies are as follows:

WBC: 7,500/mm³ (4,500-11,000)

Hemoglobin: 15.1 g/dL (13.5-17.5)

Hematocrit: 45% (41-50)

Platelets: 250,000/mm³ (150,000-450,000)

TSH: 2.1 µIU/mL (0.4-4.0)

Basic metabolic panel: within normal limits