MAPT and Alzheimer disease: In addition to AD, aggregation of hyperphosphorylated tau in the brain is also seen in several other neurodegenerative diseases, such as progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17), Pick's disease (PiD), Down syndrome (DS), postencephalitic Parkinsonism, and Niemann-Pick disease.