Background: Autoimmune encephalitis is being diagnosed more and more often in the pediatric age group. It should be suspected in children with psychiatric symptoms, encephalopathy, abnormal movements or epileptic seizures. The most frequent autoimmune encephalitis in the pediatric is anti-N-methyl-D-aspartate (anti- NMDA) receptor encephalitis. 
Case report: We report a four-year-old boy with encephalitis signs and symptoms and focal tonic-clonic seizures followed by behavior disorders. CSF and MRI results were normal; but in view of EEG showing delta waves, possibility of autoimmune encephalitis was considered. Then child was treated with plasmapheresis and symptoms were disappeared.
Conclusion: Autoimmune encephalitis is a treatable disorder and there might be a negative result in patient’s CSF antibody’s panel of autoimmune encephalitis. Electroencephalogram validated the diagnosis in this case. Considering the fact that autoimmune encephalitis is curable disorder, we recommend that the process of treatment
should be started if strong clinical suspicions exists.