Tau immunostaining revealed changes consistent with an Alzheimer's disease neuropathological score of “low” according to 2012 National Institute on Aging‐Alzheimer's Association guidelines.18 Thus, although not ruled out, a definite diagnosis of Alzheimer's disease could not be made, and the cause for his dementia could not be established. Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.