The ability to define neuronal α-synuclein disease on the basis of its biology rather than its syndromic presentation follows from the development of a new enabling technology—accurate neuronal α-synuclein seed amplification assays in CSF. In addition to a biological definition, Simuni and colleagues1 propose an integrated staging system (neuronal α-synuclein disease integrated staging system; NSD-ISS) that has close parallels to the staging in the 2018 NIA-AA research framework.4 Biological staging (or ATN biomarker profiles) in the NIA-AA research framework was based on the concept that a characteristic sequence of pathophysiological events exists that can be captured by biomarkers. Another recent advancement in the Alzheimer's disease field is the development of plasma biomarkers, some of which have diagnostic accuracy equivalent to approved CSF assays.8–10 The convergence of high-quality plasma diagnostic assays, which are far more accessible than PET or CSF, with approved disease targeted therapeutics is projected to transform patient care for Alzheimer's disease.