Definition:

Narcolepsy is a disabling sleep disorder characterized by irresistible excessive daytime sleepiness and cataplexy, a condition triggered by strong emotions leading to a sudden loss of muscle tone. Narcolepsy is a rare and mainly sporadic disorder. Familial narcolepsy accounts for less than 10% of all narcolepsy cases, and causative mutations have not been identified to date. The discovery of hypocretin-1 (HCRT) deficiency shed light on the underlying pathophysiology of the disease. The hypocretin neurotransmission system was shown to play a major role in controlling vigilance states. Because of the strong HLA association, hypocretin deficiency is believed to be caused by an autoimmune attack. It has also been reported that a missense mutation in myelin oligodendrocyte glycoprotein (MOG) is the cause of narcolepsy.