MAPT and Alzheimer disease: In AD, this is conceptualized as the ATN sequence, where β-amyloidosis [A] is thought to precede and accelerate tau pathology [T] that leads to neurodegeneration [N] [10], now expanding towards an ATX(N) system, where X represents novel candidate biomarkers for additional pathophysiological mechanisms such as neuroimmune dysregulation, synaptic dysfunction or blood-brain-barrier alterations [11].