Seasonal Factors and the Onset of Narcolepsy

Narcolepsy is caused by a selective loss of the hypocretin-producing neurons in the hypothalamus. Because most patients with narcolepsy carry the human leukocyte antigen DQB1*0602 allele, researchers have long hypothesized that the hypocretin neurons are killed by an autoimmune process, possibly triggered by infection with Streptococcus or a virus. Supporting this perspective, some patients have increased anti-streptococcal titers around the onset of narcolepsy, and new cases of narcolepsy were increased 6- to 9-fold in DQB1*0602-positive children in Finland and Sweden who received an adjuvanted H1N1 influenza vaccine. Although these findings are suggestive, direct evidence for autoimmunity in the vast majority of narcolepsy patients has be…