MAPT and Alzheimer disease: It is, for example, possible that the early increase in P‐tau reflects a neuronal reaction to the amyloidosis, rather than actual neurofibrillary tau pathology (Mattsson et al, 2017b; Sato et al, 2018), or that increased neuronal activity and secretion of a variety of intra‐neuronal proteins could be an early AD event (Cirrito et al, 2008; Li et al, 2013).