When do you suspect an autoimmune encephalitis in a child or adolescent with new-onset psychosis?

Given the rarity of true childhood schizophrenia, autoimmune encephalitis, and other medical etiologies should be considered in any patient presenting with new-onset psychosis prior to age 13. In adolescents, sudden onset of symptoms, absence of family history, lack of prodrome, and other atypical presentations suggest the need for further evaluation. While there are several types of autoimmune encephalitis, anti-NMDA receptor encephalitis is most likely to present initially with psychiatric sym...

New-onset psychosis prior to age 12-13 is rare, and alternative diagnoses should be considered more carefully. That being said, isolated psychosis in AE is also rare. The CONNECT multicenter pediatric NMDARE consortium published on this, and we found that only 5% patients presented with isolated psychiatric symptoms. Paraclinical signs of neuroinflammation from MRI, CSF, and EEG support the diagnosis. I suggest referring to the diagnostic criteria by Cellucci et al., PMID 31953309 as a general g...

Autoimmune encephalitis (AIE) has a subacute onset. While neuropsychiatric symptoms may be the presenting feature, other signs of neurological dysfunction will typically develop over time. These include focal neurological findings, movement disorders, autonomic instability, and seizures. EEG can be helpful in distinguishing from a pure psychiatric presentation from an encephalitis presentation, as the EEG will show background slowing with or without delta brushes and epileptiform discharges in A...