Seronegative Autoimmune Encephalitis: A Case Report and Literature Review on Psychiatric Presentations

Autoimmune encephalitis (AE) is an immune-mediated disorder that may present with prominent psychiatric symptoms, posing diagnostic challenges, particularly in seronegative cases. We report a 57-year-old male presenting with acute behavioral changes, psychosis, and cognitive impairment, initially managed in a psychiatric setting without clinical improvement. Subsequent evaluation revealed EEG abnormalities and elevated cerebrospinal fluid (CSF) protein, while autoimmune antibody panels were negative, leading to a diagnosis of seronegative probable AE. The patient showed marked clinical improvement following immunotherapy. This case highlights the importance of considering AE in patients with atypical psychiatric presentations, particularly when accompanied by cognitive decline or neurological findings. At the same time, careful clinical judgment is essential, as overdiagnosis and indiscriminate testing may lead to unnecessary interventions. Early recognition, guided by clinical red flags and supported by objective findings, remains critical for optimal outcomes.