Background: Anti-NMDAR encephalitis is an autoimmune disorder characterized by memory deficit, decreased level of consciousness, autonomic dysfunction and movement disorders. It occurs commonly in children and young adolescent .We report 2 cases with anti-NMDAR encephalitis presented to the pediatric emergency department at King Khalid University Hospital(KKUH).To our knowledge this is the first report from Saudi Arabia.

Case (1):A 4-year-old girl presented with sudden onset of seizure and behavioral changes followed by deterioration in her mental status and  abnormal movements . Her Clinical Examination revealed normal  vital signs, poor social interaction, Oro-facial dyskinesia, chorioathetosis  and dystonia . Brain MRI was unremarkable .Electroencephalography( EEG) showed delta slowing . Cerebrospinal fluid (CSF) analysis was negative for infection. Anti-NMDAR antibodies was positive in both serum and CSF.Screening  for underlying malignancy was negative.Marked improvement was noted  after treatment with corticosteroid ,intravenous immunoglobulin ( IVIg) and rituximab.

Case (2): A 6- year-old girl  presented with five days history of behavioral changes and insomnia associated with fluctuation in the level of consciousness  and  involuntary movements .Her clinical examination revealed minimally interactive,autonomic manifestations,oro-facial dyskinesia and chorioathetosis. MRI brain was unremarkable,EEG showed diffuse delta slowing .CSF analysis was negative for infection. Anti-NMDAR antibodies  was positive in both serum and CSF.Screening for underlying malignancy was negative.She was given IVIg ,corticosteroid and rituximab and showed marked improvement .

Conclusion: Anti-NMDAR encephalitis is  a new,under-recognized disorder.Early recognition and high index of suspicion is very important in initiation of different modality of treatments which lead to  favorable outcome.