1367 Hypersomnia in a Patient with Langerhans Cell Histiocytosis

Abstract Introduction Idiopathic hypersomnia (IH), hypersomnia due to a medical disorder, and Narcolepsy type II (NT2), including narcolepsy due to a medical disorder present with daytime sleepiness, excessive nocturnal sleep, and napping. These disorders lead to significant impairment in functioning and decreased quality of life. While there are treatments for IH and NT2, there are no medications yet approved for hypersomnia due to a medical disorder. Report of case(s) A 19 year old female with neurodegenerative Langerhans Cell Histiocytosis (LCH), epilepsy, and ADHD presented for evaluation of excessive daytime sleepiness (EDS) (ESS 22) and symptoms of sleep disordered breathing, despite adequate nocturnal sleep and amphetamine/dextroamphetamine 50 mg. Exam was significant for somnolence and grade 4 tonsillar hypertrophy. PSG demonstrated moderate OSA (OAHI 17.2/hr). She was referred for T&A and started on PAP therapy in the interim, with adequate treatment at follow up. Other studies included brain MRI which showed thickening of the anterior hypothalamus due to LCH, and CSF studies with normal hypocretin level 388 pg/mL. Post operative PSG was normal (OAHI 0.9/hr) but there was no improvement in sleepiness (ESS 21). Actigraphy showed nocturnal sleep of 9.55 hours with daytime naps resulting in an average of 11.62 hours of sleep in 24 hours. MSLT showed sleep on 4/5 naps with average SOL of 9.6 minutes with 1 SOREMP. However, MSLT was invalid due to sleep between naps. Additionally, she was medically unable to wean from all REM suppressing medications (olanzapine and timolol). At this point our differential included IH, hypersomnia due to a medical disorder, and NT2 (possibly due to a medical disorder) with diagnosis masked by REM suppression. Our working diagnosis is IH based on actigraphy criteria but other conditions cannot be ruled out. She was started on 3 g once a night of calcium, magnesium, potassium, and sodium oxybates. After titrating to the final dose of 3.5g, the patient had dramatic improvement with her EDS (ESS 2). Conclusion This patient’s diagnostic testing make a definitive categorization of her hypersomnia difficult, but the clinical picture was consistent with central disorder of hypersomnolence and she showed significant improvement with appropriate treatment. Support (if any)