MAPT and early-onset autosomal dominant Alzheimer disease: Alzheimer disease (AD), the most common neurodegenerative disease, is characterized by the accumulation of β-amyloid (Aβ) plaques, tau tangles,1 neurodegeneration, and cognitive loss.2, -, 4 Different pathophysiologic processes can be monitored in AD using biomarkers in CSF and plasma.5,6