Screening Autoimmune Anti-neuronal Antibodies in Pediatric Patients with Suspected Autoimmune Encephalitis

BACKGROUND AND PURPOSE The aim of this study was to identify and describe the pediatric autoimmune encephalitis cases positive for anti-neuronal antibody tests. METHODS Screening of six anti-neuronal antibodies in 23 children with suspected autoimmune encephalitis was performed by cell-based indirect immunofluorescence test with patients' serum or cerebrospinal fluid. RESULTS Among the 23 cases enrolled here, eight patients (35%) were positive for the anti-N-methyl-d-aspartate (NMDA) receptor antibody and one patient (4%) was positive for the anti-contactin-associated protein-like 2 (CASPR2) antibody. In the anti-NMDA receptor antibody-positive group, seizure and movement disorders were the most prominent features and were present in all patients. A tumor was present in only one patient. Three patients with infant- and toddler-onset disease did not exhibit a classic multistage illness. In addition to seizure and dyskinesia, aphasia or mutism without severe consciousness impairment was present in all three patients. These atypical clinical presentations may suggest different pathomechanism of anti-NMDA receptor encephalitis among these age groups. The patient who was positive for the anti-CASPR2 antibody was an 8-year-old girl who presented with fever, encephalopathy, and seizure. Neuromyotonia or other dyskinesia was not present. CONCLUSIONS Eight anti-NMDA receptor antibody positive patients and one CASPR2 positive patient were identified from the screening of six anti-neuronal antibodies in pediatric patients suspected with autoimmune encephalitis. Developmental regression specifically for language skills was suggested as one of the atypical clinical features in infants and toddler onset anti-NMDA receptor antibody positive patients.