MAPT and early-onset autosomal dominant Alzheimer disease: Alzheimer’s disease (AD) is the leading cause of dementia.1,2 It is a proteinopathy characterized by a progressive decline in cognitive function and the accumulation of the Amyloid βeta and Tau in the brain (AD hallmark).3 The cerebrospinal fluid (CSF) proteins amyloid βeta1–42 (Aβ42), Tau, phosphorylated tau (pTau), and the Tau/Aβ42 ratio (TAR) are considered accurate measures that reflect those brain pathologies.4 However, despite the significant efforts put into developing treatments that target the accumulation of Aβ and Tau, the treatment of AD remains a significant challenge.