FTDP-17 is a heterogenous clinical pathologic entity that can now be defined by the presence of causative mutations in the tau gene (as described subsequently). As the name implies, the clinical picture is dominated by frontal-temporal dementia and parkinsonism. Different FTDP-17 syndromes have been described, and pheno-typic differences may reflect differences in regional distribution of tau pathology and degeneration in the brain (15).
While the pathology of FTDP-17 can be varied, even between different members of the same family, all cases of FTDP-17 are unified by the presence of severe filamentous hyperphosphorylated tau pathology in neurons, with accompanying regional neuronal loss (39-44). Glial involvement by tau pathology (similar to that seen in CBD and PSP) is seen in some but not all FTDP-17 cases.
Despite the fascinating phenotypic, genetic, and pathologic diversity seen in FTDP-17 cases, these cases are all defined by an insidious cascade in which pathogenic mutations in the tau gene lead to tau dysfunction and/or accumulation of brain tau pathology, which in turn lead to neurodegeneration.
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