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- Disorder of unknown etiology characterized by excessive daytime sleepiness typically associated with cataplexy (sudden bilateral weakness of skeletal muscles) and other REM sleep phenomena, such as sleep paralysis and hypnagogic hallucinations (e.g., vivid auditory or visual perceptions without an external stimulus that occur as one is falling asleep)
- Commonly misconceived as representing low intelligence and/or poor motivation
- Frequently overlooked disorder, with an average of 15 years of symptoms prior to diagnosis
- System(s) affected: Nervous
- Onset usually in teenage years
- Bimodal distribution peak at 15 and 36 years of age
- Predominant sex: Male > Female (1.6:1)
- Occurrence: 0.74/100,000 persons
Uncommon in childhood
25–50 cases/100,000 people.
- Head trauma
- CNS infectious disease
- Psychological stress
- Family history
- High BMI
- Increased incidence in families with positive history: 1–2% in 1st-degree relative of index case (10–40× the general population)
- Twin concordance is 25–31% (suggests environmental contribution)
- Most are sporadic.
- 85–95% of patients with narcolepsy and cataplexy have biologic HLA DQB1*0602; 40% of patients with narcolepsy without cataplexy express this antigen. (HLA) DQB1*0602 is present in 24% of the general population.
- Autosomal-recessive inheritance pattern
- 12% of Asians, 25% of whites, and 38% of African Americans are gene carriers.
- Neurodegenerative disorder resulting from selective loss of neurons containing hypocretin in the hypothalamus; may be autoimmune (associated with influenza A or Strep. pyogenes)
- 85% of patients with narcolepsy and cataplexy have low hypocretin in CSF.
- Possible involvement of immune system and environmental influences
Commonly Associated Conditions
Obstructive sleep apnea, obesity, anxiety