In contrast to well established and generally accepted pattern of the cerebrospinal fluid (CSF) biomarkers for the diagnosis of Alzheimer’s Disease (AD), which includes decreased values of Aβ1-42 and Aβ42/40, and increased concentrations of Tau and pTau181 (Lewczuk et al. 2018; Hansson et al. 2019), the diagnostic role of α Synuclein (αSyn) in Parkinson's Disease (PD) and Dementia with Lewy Bodies (DLB) is still a matter of debate. The gene discussed is MAPT; the disease is Alzheimer disease.