Four Narcolepsy Cases after H1N1 Infection or Vaccination

Narcolepsy was known as a disease caused by loss of hypocretin cells in the hypothalamus, might be an autoimmune disorder or involve an infectious agent with participation of immune system.1 The diagnostic criteria of narcolepsy according to the third edition of International Classification of Sleep Disorders-3 is: 1) The patient has daily periods of irrepressible need to sleep or daytime lapses into sleep occurring for at least three months. 2) The presence of one or both of the following: (1) Cataplexy (as defined under Essential Features) and a mean sleep latency of ≤ 8 minutes and two or more sleep onset rapid eye movement (REM) periods (SOREMPs) on an multiple sleep latency tests (MSLT) performed according to standard techniques. A SOREMP (within 15 minutes of sleep onset) on the preceding nocturnal polysomnogram may replace one of the SOREMPs on the MSLT. (2) Cerebrospinal fluid (CSF) hypocretin-1 concentration, measured by immunoreactivity, is either ≤ 110 pg/mL or <1/3 of mean values obtained in normal subjects with the same standardized assay. The mechanism seems to be associated with human leukocyte antigen (HLA), T-cell receptor polymorphisms and recently reported Tribbles 2 autoantibodies.2 However, only 1–2% of first degree relatives of narcoleptics develop the disease and 70–75% of monozygotic twins are discordant for the disorder, suggesting strong environmental influence.3,4 Previous studies proposed Streptococcal infections as probable environmental trigger for narcolepsy.5 We report 4 cases of narcolepsy that were developed after Influenza A/H1N1 infection or vaccination who had neither previous medicosurgical nor neuropsychiatric history.