MAPT and early-onset autosomal dominant Alzheimer disease: Among brain disorders, the Alzheimer’s disease (AD) field is in the good situation that a panel of cerebrospinal fluid (CSF) biomarkers is at hand, including the 42 amino acid variant of β-amyloid (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau), and have in numerous studies been shown to have high diagnostic accuracy for AD also in the early stage of the disease (1).