Autoimmune encephalitis in children: Frequency, clinical spectrum and antibody profile at a tertiary care center in northern India.

Background

Autoimmune encephalitis (AE) is one of the treatable cause of pediatric encephalitis and is increasingly being recognised as area where timely detection and treatment can limit significant morbidity in such patients. However, data on its occurrence in Indian children remain limited.

Objectives

To determine the proportion of AE among acute encephalitic syndrome (AES) cases and characterise the clinical and antibody profile in children.

Methods

This observational cross-sectional study was conducted from May 2023 to October 2024 in a tertiary care hospital in northern India. Children aged one month to12 years with AES were screened for AE using Graus criteria. Cerebrospinal fluid and/or serum antibodies against neuronal antigens (NMDAR, AMPAR1/2, CASPR2, LGI1, GABARB1/B2) were detected using indirect immunofluorescent assay with HEK-293 transfected cells. All children were classified into possible, definite antibody positive and probable antibody-negative paediatric AE as per established definitions.

Results

Of 188 children with AES, 50 (26.5%) met criteria for possible AE. After excluding two Parvovirus B19-positive cases, 48 children (25.5%) underwent antibody testing. Four children (8.3% of possible AE; 2.1% of all AES) tested positive for anti-NMDAR antibodies. Additionally, four cases (8.3%) were identified as probable antibody-negative AE. Common presentations included seizures (70.8%), focal neurological deficits (31.2%), and altered mental status (29.2%). All laboratory-confirmed cases were anti-NMDAR positive.

Conclusion

All AE cases diagnosed in the study were anti-NMDAR (N-Methyl-D-aspartic acid receptor) positive encephalitis. A significant proportion of possible/probable AE cases remain non-reactive with the testing antibody panel suggesting undiscovered antigens. Routine antibody screening should be considered in all microbiologically negative AES cases.