Although it is possible that some of our participants with abnormal amyloid biomarkers and low CSF p-tau levels had an additional non-Alzheimer’s disease cause of their cognitive impairment, 5 of these 12 participants underwent tau PET, all of which were unequivocally positive (mean SUVR 2.05). Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.