MAPT and Alzheimer disease: In AD, CSF biomarkers have been recognized to reflect the prevailing hypothesis for its pathogenesis and the typical biochemical profile is a decrease of Aβ42 levels, which is considered to reflect amyloidogenesis, as well as an increase of total tau (T-tau) and phosphorylated tau (P-tau), which reflect axonal degeneration and tangle formation [3,4].