HLA-DB0602, a genetically-encoded protein that conveys to those that possess it a higher risk of developing narcolepsy.
Narcolepsy[Etym. n. 1] is a sleep disorder that is considered a tetrad (i.e., combination of four) of symptoms, for one it causes excessive daytime sleepiness and in some people it may cause them to involuntarily fall asleep at random times during the day. Another defining characteristic and member of this diagnostic tetrad is cataplexy (present in 50-90% of patients with the disorder), which is the involuntary loss of muscle tone (i.e., muscle weakness) potentially to the point of paralysis or collapse whilst being conscious, that is triggered by emotional triggers such as happiness, pleasure, laughter, etc. Additional members of this tetrad include: hallucinations that occur either soon after awakening or soon before going to sleep and sleep paralysis which occurs when falling asleep or awakening and is characterized by being unable to move one's voluntary muscles including those controlling one's eyes, despite being conscious.
The aetiology of narcolepsy is not entirely known, but an autoimmune component is suspected based on genetic studies showing that mutations in Human Leukocyte Antigen (HLA) genes influence one's risk of developing the disorder. It is believed to be the result of an autoimmune response directed against the hypocretin (orexin)-secreting neurons in the hypothalamus. Hypocretin regulates the body's sleep-wake cycle by binding to its own receptors.
Its treatment is purely symptomatic (i.e., managing the symptoms, without affecting the underlying cause) and involves psychostimulants like dexamfetamine, methylphenidate and modafinil for excessive daytime sleepiness, along with tricyclic antidepressants (TCAs) and sodium oxybate (also known as gamma-hydroxybutyrate [GHB]) for cataplexy and TCAs for sleep paralysis/hallucinations.
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- ↑ Narco- comes from the Ancient Greek and pertains to sleep or numbing, e.g., narcotic originally referred to drugs that place one into a sleep-like state, namely the opioids like morphine. -lepsy also comes from the Ancient Greek and means seizure, taking, possession, etc.
- ↑ Siebold, C; Hansen, BE; Wyer, JR; Harlos, K; Esnouf, RE; Svejgaard, A; Bell, JI; Strominger, JL; Jones, EY; Fugger, L (17 February 2004). "Crystal structure of HLA-DQ0602 that protects against type 1 diabetes and confers strong susceptibility to narcolepsy.". Proceedings of the National Academy of Sciences of the United States of America 101 (7): 1999-2004. doi:10.1073/pnas.0308458100. PDB: 1UVQ (RCSB PDB, PDBe). PMC 357041. PMID 14769912.
- ↑ 2.0 2.1 2.2 2.3 Willacy, H (28 March 2013). Knott, L; Jackson, C, ed. "Narcolepsy and Cataplexy". Patient.co.uk Professional Reference. Green Lane, UK: Egton Medical Information Systems Limited. Retrieved 20 November 2014.
- ↑ 3.0 3.1 De la Herrán-Arita, AK; García-García, F (2014). "Narcolepsy as an immune-mediated disease.". Sleep Disorders 2014: 792687. PMC 3914477. PMID 24551456. doi:10.1155/2014/792687.
- ↑ Kumar, S; Sagili, H (February 2014). "Etiopathogenesis and neurobiology of narcolepsy: a review.". Journal of Clinical and Diagnostic Research 8 (2): 190–5. PMC 3972560. PMID 24701532. doi:10.7860/JCDR/2014/7295.4057.