Developmental Regression and Seizures in a 28-Month-Old Child: A Delayed Diagnosis of Anti-N-Methyl-D-Aspartate Receptor Encephalitis.

Anti-N-methyl-D-aspartate (anti-NMDA) receptor encephalitis is a diagnostic challenge. Delayed treatment may result in irreversible neurological complications and can even be life-threatening if pediatricians do not recognize it early and manage it comprehensively. We report the case of a 28-month-old child whose diagnosis was initially missed, even at a level 1 children's hospital, because there were no significant changes on brain magnetic resonance imaging (MRI), cerebrospinal fluid analysis (CSF), or electroencephalography (EEG), despite developmental regression and seizures. We conclude that autoimmune encephalitis should be kept in mind even when imaging and other diagnostic tests show no significant abnormalities. Eventually, the patient was successfully treated with immunotherapy. This case highlights the importance of early diagnosis and treatment, as well as the strong correlation between medical history, clinical progression, and diagnostic findings, and the need for suspicion even when initial investigations are inconclusive.