Limbic encephalitis caused by herpes simplex virus infection after vaccination against the influenza virus

Abstract Various causative factors, including viral infection, autoimmunity, and paraneoplasia, are considered to be involved in the pathomechanism of limbic encephalitis. We encountered a patient who developed limbic encephalitis after vaccination against the influenza virus. In Japan, an influenza epidemic occurs every winter, and vaccination against the influenza virus is recommended. However, there have been reports of serious side effects such as the development of Guillain-Barre syndrome and acute disseminated encephalomyelitis after influenza vaccination; these findings indicate the activation of an autoimmune pathomechanism after vaccination. Here, we discuss the relationship between limbic encephalitis and influenza vaccination from the perspective of viral infection and autoimmunity. We considered that limbic encephalitis was caused by the herpes simplex virus, and hypothesized that this clinical condition rarely develops as a sole consequence of influenza vaccination but rather develops because of the activation of an autoimmune pathomechanism after vaccination.