Acute flaccid paralysis as an unusual presenting symptom of Japanese encephalitis: a case report and review of the literature

Japanese encephalitis (JE) is an endemic disease in Taiwan. Acute JE virus infection characterized by acute flaccid paralysis in an adult has never been reported in Taiwan. We report a young adult man who received four doses of JEV (Nakayama strain) vaccination in childhood, but still developed acute JE virus infection, characterized with acute flaccid paralysis.He presented with fever, headache, progressive muscle weakness, and respiratory paralysis requiring mechanical ventilator. Deep tendon reflexes were decreased except for the Achilles reflex. After supportive care, he was weaned from the mechanical ventilator and at discharge 1 month later, his muscle power level and deep tendon reflexes recovered partially. The diagnosis of JE was based on the presence of anti-JE virus IgM in the CSF and seroconversion of IgM and IgG by the ELISA method. Electrophysiological findings were described. From the experience of this case, we caution that a history of vaccination for JE with the Nakayama strain may not provide a complete protection against natural infection in the community; and in Taiwan or any area where JE remains an endemic disease, Japanese virus encephalitis infection should be considered as a differential diagnosis in any adult presenting with acute flaccid paralysis.