MAPT and Alzheimer disease: Corticobasal degeneration (CBD) pathology gives rise to a variety of clinical presentations that encompass (1) the classic presentation, known as corticobasal syndrome (CBS); (2) a syndrome similar to progressive supranuclear palsy (CBD-PSP); (3) a frontotemporal behavioral variant; and (4) a variant with progressive nonfluent aphasia (CBD-PNFA).1 However, clinical symptoms similar to the ones described above can also be caused by PSP, Alzheimer disease (AD), and non-tau pathologies, making an accurate prediction of the underlying pathology difficult in vivo.2,3