Frontotemporal dementia: An updated overview

Frontotemporal dementia (FTD) is a progressive neurodegenerative syndrome occurring between 45 and 65 years. The syndrome is also called frontotemporal lobar degeneration (FTLD). However, FTLD refers to a larger group of disorders FTD being one of its subgroups. The other subgroups of FTLD are progressive nonfluent aphasia (PFNA), and semantic dementia (SD). FTLD is characterized by atrophy of prefrontal and anterior temporal cortices. FTD occurs in 5-15% of patients with dementia and it is the third most common degenerative dementia. FTD occurs with equal frequency in both sexes. The age of onset is usually between 45 and 65 years though it may range anywhere from 21 to 81 years. The usual course is one of progressive clinicopathological deterioration with mortality within 6-8 years. Unlike Alzheimer's disease (AD), this condition has a strong genetic basis and family history of FTD is seen in 40-50% of cases. FTD is a genetically complex disorder inherited as an autosomal dominant trait with high penetrance in majority of cases. Genetic linkage studies have revealed FTLD loci on chromosome 3p, 9, 9p, and 17q. The most prevalent genes are PGRN (progranulin) and MAPT (microtubule-associated protein tau), both located on chromosome 17q21. More than 15 different pathologies can underlie FTD and related disorders and it has four major types of pathological features: (1) microvacuolation without neuronal inclusions, (2) microvacuolation with ubiquitinated rounded intraneuronal inclusions and dystrophic neurites FTLD-ubiquitinated (FTLD-U), (3) transcortical gliosis with tau-reactive rounded intraneuronal inclusions, (4) microvacuolation and taupositive neurofibrillary tangles. Behavior changes are the most common initial symptom of FTD (62%), whereas speech and language problems are most common in NFPA (100%) and SD (58%). There are no approved drugs for the management of FTD and trials are needed to find effective agents. Non-pharmacological treatment and caregiver training are important in the management of FTD.