Both neurological and psychiatric symptoms are observed among mental disorders and represent a challenge for the differential diagnosis, specially in old adults presenting behavioral changes. Investigations have documented manic/hypomanic symptoms from behavioral variant frontotemporal dementia(bvFTD), suggesting a relationship of bipolar disease (BD) with bvFTD.

This work aims to determine the relationship between patients with bipolar disease and behavioral variant frontotemporal dementia.

A non-systematic review of the literature is presented. Bibliographic selection was carried out through keyword research in MEDLINE and Google Scholar.

An early stage of bvFTD often displays a mix of behavioral disturbances and personality changes. Also, BP is associated with a higher risk of dementia in older adults and with cognitive impairment, where a subset of patients presents a neuroprogressive pattern during the disease course. It was shown a specific type of post-BD dementia with clinical features of bvFTD and cases of patients with marked manic symptoms for the first time in their life had subsequent diagnosis of FTD. Mutations in the progranulin gene (GRN) were the most frequent causes of autosomal dominant FTD and have also been reported in sporadic FTD. Genetic polymorphisms in this gene are also associated with schizophrenia and BD. An hypothetical model of shared mechanisms between bvFTD and BD was proposed, including specific mendelian mutations associated with genetic predisposition (e.g. brain-derived neurotrophic factor-BDNF gene) and environmental factors with an effect on cellular homeostasis (e.g. increased cell deaths, decreased synthesis of synaptic proteins) and an influence over behavioural and cognitive symptoms. Nevertheless, comparison of the executive functions, social cognition profiles and structural neuroimaging of bvFTD and elderly patients with BD showed difference in patterns.

Although BD is principally considered a neurodevelopment disorder, while FTD is a neurodegenerative disorder, follow-up studies of cognitive deficits, imaging, and genetics in BD patients could elucidate the possible correlation between these major diseases and may have implications for pathogenesis, as well as for treatment.