Background: This study was aimed to identify and describe pediatric cases of autoimmune encephalitis confirmed by autoimmune synaptic antibodies tests.

Methods: From July 2011 to May 2013, acute encephalitis patients who were tested for NMDAR, LGI1, CASPR2, AMPA1/AMPA2, and GABA-BR were included. All patients who met all of the following criteria were enrolled; immunocompetent, acute onset encephalopathy, no proven etiology by initial screening.

Results: Among 20 enrolled cases, six patients (30%) were positive for NMDAR antibody and one patient (5%) was positive for CASPR2. The mean age of NMDAR Ab+ patients was 9.7 years (range, 2-16) and four of them (67%) were female. Two patients experienced prodromal illness such as fever, headache, or respiratory symptoms. All patients showed early onset of seizure, and some of them showed dyskinesia(5/6, 83%), psychosis(3/6, 50%), language disturbance(4/6, 67%) or autonomic instability(3/6, 50%) in the hospital course. Only one had a tumor, unilateral ovarian teratoma. All patients received steroid and intravenous immunoglobulin and 2 patients received adjunctive rituximab. Mean follow-up period was 10 months (range, 4-18 months), and none of the patients had significant sequalae. The patient with positive CASPR2 antibody was 8 years old girl, with similar clinical course and treatment outcome with NMDAR+ patients.

Conclusion: Anti-NMDA receptor encephalitis was the most common cause of autoimmune encephalitis. Multistage illness and favorable response to immunotherapy in all patients were in line with previous studies. We also identified the first pediatric case of anti-CASPR2 encephalitis, expanding the spectrum of pediatric autoimmune encephalitis