MAPT and Schnyder corneal dystrophy: Studies have demonstrated that an increase in CSF tau and p-tau is a specific sign of AD progression that occurs downstream of the deposition of Aβ [105] and CSF p-tau was a significant predictor for PET-amyloid in SCD (subjective cognitive decline), MCI, and dementia [106].The time order of some biomarker changes is as follows CSF Aβ→CSF P-tau→CSF T-tau→PET Aβ−→PET tau.