Nationwide survey of acute juvenile female non-herpetic encephalitis in Japan: relationship to anti-N-methyl-D-aspartate receptor encephalitis.

Objective: To study the incidence and clinical features of acute juvenile female non-herpetic encephalitis (AJFNHE) in Japan.
Methods: A nationwide questionnaire on patients with severe non-herpetic encephalitis of unknown etiology with a prolonged clinical course or death was sent to the departments of Internal Medicine, Neurology, Pediatrics, and Emergency and Critical Care at all hospitals with 200 beds or more in Japan.
Results: The recovery rate was 25% (1,279 out of 5,030 departments) and 90 patients were enrolled in this study. The annual incidence was 0.33/10(6) population. 85% of patients were female. The means and standard deviations of age at onset and hospital stay were 26+/-10 years and 180+/-228 days. As first symptoms, fever and psychosis were presented in 90%. Among the neurological symptoms, disturbance of consciousness was presented in 92%, convulsions in 65%, and involuntary movements in 55%. Respiratory failure during hospitalization was observed in 71% and required care with mechanical ventilation. The detection rate of anti-GluR epsilon2 and/or delta1 antibodies was 67% of patients. Anti-N-methyl-D-aspartate receptor NR1/NR2 antibody was detected in all four examined patients with anti-GluR epsilon2 antibody, and also detected in both of the two examined patients without anti-GluR epsilon2 antibody. As for outcome, 46% returned to work and 37% returned home, but 7% died. Associated tumors were demonstrated in 39%. All reported patients had ovarian tumors, among which teratoma was the most frequent.
Conclusion: A nationwide survey provided data for the annual incidence and clinical features of AJFNHE in Japan.