Paranoid personality masking an atypical case of frontotemporal dementia.

Frontotemporal dementia (FTD) is a debilitating disease that is well described in the "Diagnostic and statistical manual of mental disorders, fifth edition (DSM-5)", and typically presents with memory impairment, progressive decline in cortical functioning, and behavioral changes. Age of onset is generally in the late fifties, and usually the first presentation involves a change in behavior and emotional blunting. Treatment of FTD involves management of any neurobehavioral symptoms while trials of atypical antipsychotics are ongoing but suggest some efficacy. We present a case of a patient who first presented with severe paranoid personality traits and frank persecutory delusions. This atypical presentation of our patient first led to her incorrect diagnosis of a psychotic disorder and paranoid personality disorder. As a result of this diagnosis, she was treated unsuccessfully. A subsequent magnetic resonance imaging (MRI) then showed atrophy of frontal and temporal lobes bilaterally (left more prominent than right) which confirmed the diagnosis of FTD. The importance of this case involves the atypical presentation of paranoia and delusions, and our patient's incorrect diagnosis based on her clinical presentation led to a trial of unsuccessful treatment. Only after performing an MRI, which showed atrophy, was the patient appropriately treated and deemed medically stable. This case report illustrates the importance of considering a rare presentation of frontotemporal lobe dementia with patients who are in the typical age range and present with paranoia and delusions.