Cerebrospinal fluid levels of total tau, phosphorylated tau 181 (p-tau181), and amyloid beta 1-42 (Aβ42) have been studied for more than 30 years for the diagnosis of AD pathology (249), especially as an early diagnostic tool and eventually incorporated into the diagnostic criteria of AD in 2018 (207). The gene discussed is MAPT; the disease is Alzheimer disease.