There are several primary tauopathies, such as argyrophilic grain disease (AGD), Creutzfeld–Jakob disease (CJD), and corticobasal degeneration (CBD), in which tau alterations play a central role in neurodegeneration (Table 1); however, as the incidence of these diseases is lower than that of secondary tauopathies, this review will focus on secondary tauopathies. The gene discussed is MAPT; the disease is tauopathy.