MAPT and early-onset autosomal dominant Alzheimer disease: Efforts to use α-synuclein measurements for disease differentiation have been largely inconclusive, with plasma measurements considered of limited value due to the protein's extensive peripheral expression, particularly in erythrocytes.16,17 Nevertheless, parallels can be drawn with Tau protein in Alzheimer’s disease, which, despite its peripheral expression, reflects brain-specific pathological processes such as truncation and phosphorylation.18-21 This raises the possibility that α-synuclein could similarly serve as a marker of central nervous system pathology under appropriate conditions.