MAPT and early-onset autosomal dominant Alzheimer disease: Established (classical) biomarkers of dementia in the cerebrospinal fluid (CSF), namely amyloid beta with 42 amino acids (Aβ42), a marker of amyloid pathology (plaque formation), total tau protein (τT), a non-specific marker of neurodegeneration and neuronal/axonal loss and phosphorylated tau protein at threonine 181 (τP-181), a marker of tau pathology (neurofibrillary tangle formation) have been proven useful in the (differential) diagnosis of Alzheimer’s disease (AD) and have been incorporated in AD diagnostic criteria and guidelines [5].