Frontotemporal dementia (FTD), or frontotemporal degeneration disease, or frontotemporal neurocognitive disorder, encompasses several types of dementia involving the frontal and temporal lobes. FTDs are broadly presented as behavioral or language disorders. The three main subtypes or variant syndromes are a behavioral variant (bvFTD) previously known as Pick's disease, and two variants of primary progressive aphasia – semantic variant (svPPA), and nonfluent variant (nfvPPA).Two rare distinct subtypes of FTD are neuronal intermediate filament inclusion disease (NIFID), and basophilic inclusion body disease. Other related disorders include corticobasal syndrome and FTD with amyotrophic lateral sclerosis (ALS) FTD-ALS also called FTD-MND.
Frontotemporal dementias are mostly early-onset syndromes that are linked to frontotemporal lobar degeneration (FTLD), which is characterized by progressive neuronal loss predominantly involving the frontal or temporal lobes, and a typical loss of over 70% of spindle neurons, while other neuron types remain intact.
FTD was first described by Arnold Pick in 1892 and was originally called Pick's disease, a term now reserved only for behavioral variant FTD which shows the presence of Pick bodies and Pick cells. Second only to Alzheimer's disease (AD) in prevalence, FTD accounts for 20% of early-onset dementia cases. Signs and symptoms typically manifest in late adulthood, more commonly between the ages of 45 and 65, approximately equally affecting men and women.