Rapidly Progressive Dementia Presenting as Schizophrenia Spectrum Disorder: A Diagnostic Dilemma

Rapidly progressive dementia (RPD) presenting initially as schizophrenia spectrum disorder poses significant diagnostic challenges. We present the case of a 55-year-old woman initially diagnosed with schizophrenia spectrum disorder due to symptoms including social withdrawal, disorganized behavior, and psychosis. However, the rapid progression of cognitive decline and motor dysfunction prompted further investigation, leading to the diagnosis of anti-N-methyl-d-aspartate (NMDA) receptor antibody-mediated encephalitis. Cerebrospinal fluid analysis revealed the presence of anti-NMDA receptor antibodies, guiding targeted immunomodulatory therapy with intravenous immunoglobulin and corticosteroids. This resulted in significant clinical improvement, highlighting the importance of comprehensive diagnostic evaluation and timely initiation of immunomodulatory therapy in autoimmune-mediated RPD. This case underscores the complexities of overlapping psychiatric and neurological conditions and emphasizes the need for a multidisciplinary approach to diagnosis and management.