Case Report: Acute Psychiatric Behavioral Disturbance in a Patient with Presenilin 1 Gene Mutation Associated with Familial Alzheimer's Disease.

Familial Alzheimer's disease (FAD), often linked to presenilin 1 (PSEN1) mutations, is characterized by an autosomal dominant inheritance and earlier onset compared to sporadic Alzheimer's disease. We report a 48-year-old female patient diagnosed with early-onset FAD carrying a PSEN1 (p.Met139Leu) mutation, who initially presented with cognitive decline and later developed acute psychotic symptoms. Despite combined antipsychotic and anti-dementia treatment, her cognitive function rapidly deteriorated, resulting in significant functional loss. This case highlights the atypical early psychiatric manifestations of FAD, emphasizing the importance of genetic testing and prompt intervention in younger patients presenting with cognitive and psychiatric symptoms.