MAPT and Alzheimer disease: In particular, MAPT mutations result in a ventral degeneration pattern (initially affecting the amygdala, hippocampus, entorhinal cortex, and temporal pole) [131], whereas GRN mutations are associated with a lateral degeneration pattern [132], with frequent extension to areas not typical of bvFTD, particularly in the posterior regions, possibly for an overlap with AD pathology [133].