Narcolepsy is defined as a pentad of symptoms that include excessive daytime sleepiness, disturbed nocturnal sleep, sleep paralysis, cataplexy, and hypnagogic or hypnopompic hallucinations1. The cause of narcolepsy is still unknown, although it has been associated with a combination of genetic and environmental factors; the prevalence is approximately 0.04%2. The peak age of onset is the second decade of life, and onset after age 55 or prior to age 10 is rare. Not every symptom is present in all patients, and the severity is also variable2.
Hypocretin, a neuropeptide of hypothalamic origin, has been involved in the pathogenesis of narcolepsy. The CSF hypocretin-1 levels are very low or even undetectable in most narcoleptic patients with cataplexy. The HLA-DQB1*0602 allele, which is involved in the control of the hypocretin receptor, is also present in 88% to 98% of such patients2.
The association between narcolepsy and vaccination against the 2009 pandemic influenza A (H1N1) virus was initially suggested in 2010 in Finland and Sweden, leading to the suspension of vaccination in these countries3. Additional cases were subsequently reported,4-5.
Herein, we describe a patient with narcolepsy with cataplexy syndrome after A/H1N1 vaccination in Brazil and discuss the potential causes and treatment.