MAPT and Alzheimer disease: The National Institute on Aging-Alzheimer’s Association research framework suggested a biological definition of Alzheimer’s disease that is built on biomarkers of β-amyloid, tau and neurodegeneration aiming for more harmonized cohort studies.2 Development of efficient and personalized treatments relies on an in-depth characterization of Alzheimer’s disease heterogeneity.3 As a complement to β-amyloid and tau markers, studies of additional cerebrospinal fluid (CSF) biomarkers provide information on co-existing, inducing and/or interacting mechanisms in Alzheimer’s disease.