Patients with AD were reported to have three-fold higher CSF tau levels (Hampel et al., 2008); some considered it is a potential biomarker of AD (Lewczuk et al., 2017); and even might predict a rapid progression from mild cognitive impairment (MCI) to AD-associated dementia (van Rossum et al., 2012). The gene discussed is MAPT; the disease is Alzheimer disease.