Abstract
BACKGROUND: Autoimmune encephalitis (AE) can present as first-episode psychosis (FEP) in children. An FEP diagnostic algorithm has been proposed, but how this algorithm applies to children is unknown. We assess the FEP diagnostic algorithm in children with FEP. METHODS: The FEP algorithm was applied to a retrospective cohort of children with FEP without other neurological symptoms. RESULTS: Twenty-four patients were included, with five AE (anti-N-methyl-d-aspartate receptor encephalitis) and 19 non-AE patients (12 primary psychiatric, two headaches, mycoplasma-related encephalitis, post-coronavirus disease 2019 encephalitis, drug reaction with eosinophilia and systemic symptoms [DRESS] syndrome, cobalamin C deficiency, and two unknown). Some non-AE patients (five of 19 = 26%) received immunotherapies, with symptom resolution in one of five (20%) with immunotherapy and in four of 14 (29%) without immunotherapy. The FEP algorithm recommended cerebrospinal fluid (CSF) testing in all (five of five = 100%) patients with AE and in six of 19 (32%) non-AE patients, resulting in 100% sensitivity (95% confidence interval [CI]: 100% to 100%) and 45.5% specificity (95% CI: 16% to 75%), with a negative predictive value of 100% (95% CI: 100% to 100%). CONCLUSIONS: FEP can occur in children from different causes, including AE and metabolic conditions. Evaluation of FEP should be broad, especially without CSF evidence of inflammation. The FEP algorithm is useful to assess patients who would benefit from CSF testing and should be assessed in larger cohorts.