Finding the signal in pediatric encephalitis: promise and caution in anti-NMDAR antibody testing

The critically ill child with encephalitis presents clinicians with one of the more difficult diagnostic challenges in pediatric medicine. Fever, seizures, altered mental status, abnormal movements, behavioral changes, and autonomic instability may all evolve over hours to days, often requiring a broad differential diagnosis while awaiting testing. 1 While empiric antimicrobial therapy is frequently initiated early, the decision to pursue immunotherapy for suspected autoimmune encephalitis is more complex. Delay may worsen outcomes, yet premature treatment risks exposing children to unnecessary immunosuppression. 2 , 3 In this uncertainty, clinicians look for patterns: a distinctive clinical trajectory, suggestive EEG findings, characteristic MRI abnormalities, and, most importantly, confirmatory testing to help solidify a path forward.