1063 Difficulties in diagnosing milder forms of Kleine-Levin syndrome

The prevalence of Kleine-Levin syndrome (KLS) is 1 to 5 cases per million population. Milder forms of KLS can mimic narcolepsy, circadian rhythm disorders, idiopathic hypersomnia, and mood disorders. A 15 year old white male with no significant past medical history, psychiatric history or family history of sleep disorders presented with episodic excessive daytime sleepiness. He reported a total of six episodes, lasting 2–3 days, with two per year in 2016, 2017, and 2018. During the events, he slept 15–18 hours per day with difficulty awakening, slowed cognitive function, a sensation of derealization and depersonalization, compulsive eating and hypersexuality. In between these episodes, he returned to his baseline, sleeping for 8 hours on weekdays and 13 hours on weekends with sleep latencies of less than 30 minutes. The patient denied symptoms of depression or anxiety. His school performance was below average. The physical exam was normal except for a BMI of 32. The MRI of brain and the EEG were normal. The polysomnogram showed mild snoring, decreased sleep efficiency (83.9%), a prolonged sleep latency (48 minutes), a normal REM sleep latency (117 minutes), and decreased total REM sleep (62 minutes, 15.4%). There was no significant sleep-related breathing, periodic limb movements, nocturnal hypoxemia, or parasomnia. No seizures were seen. The multiple sleep latency test was normal. Actigraphy showed more than 16 hours of sleep a day during the episodes and 7–8 hours of sleep per day at baseline. Bedtime was delayed to between 3:00 AM to 6:00 AM regardless of whether he was in an episode or at baseline. The patient’s presentation would support the diagnosis of mild KLS, however, the shorter duration of the episodes is atypical. Confounding factors such as poor sleep hygiene and severe circadian rhythm disorder make certainty of this diagnosis more challenging.