The asymptomatic individual met the AT(N) criteria for Alzheimer’s disease (reduced CSF Aβ-42/Aβ-40 ratio 0.053, where values less than 0.065 are suggestive of fibrillar Aβ deposition; elevated CSF phospho-tau 181, 64 pg ml−1; normal range, 0–58 pg ml−1). This evidence concerns the gene MAPT and Alzheimer disease.