MAPT and Alzheimer disease: Finally, due to two previously reported cases of decreased penetrance of the PSEN1 H163Y mutation [58] (one of which was the outlier mentioned in the introduction), we report the CSF biomarker and clinical status of the six PSEN1 H163Y mutation carriers in the current study; Four of the PSEN1 H163Y mutation carriers had more than one CSF samples and all four had low levels of CSF Aβ42 and high levels of CSF t-tau and p-tau, suggesting AD pathological change and penetrance of the mutation.