At variance with Aβ42, according to our data, CSF p-tau level represents a more reliable marker of brain AD-related tau pathology since it fails to consistently discriminate between patients with or without neurofibrillary pathology only when p-tau deposition is relatively mild and limited to the transentorhinal/entorhinal cortices (Braak stages I–II). This evidence concerns the gene MAPT and Alzheimer disease.