Brief ReportsApplying the Alzheimer Disease ATN Diagnostic Framework in Atypical DementiaFunnell, Clark MD, FRCPC*; Feldman, Howard H. MD, FRCPC*,†; Mackenzie, Ian R.A. MD, FRCPC‡,§; DeMarco, Mari L. PhD, DABCC, FCACB‡,∥ Author Information *Division of Neurology, University of British Columbia ‡Department of Pathology and Laboratory Medicine, University of British Columbia §Department of Pathology and Laboratory Medicine, Vancouver General Hospital ∥Department of Pathology and Laboratory Medicine, St. Paul’s Hospital, Providence Health Care, Vancouver, BC, Canada †Department of Neurosciences, University of California San Diego, La Jolla, CA Patient consent for publication: Obtained from next-of-kin. I.R.A.M. reports personal fees from Prevail Therapeutics, outside the submitted work. H.H.F. reports UCSD service agreements for consulting with Eisai, Merck, Tau RX, Samus, Arkuda, Samumed, Axon Neurosciences, Roche/Genentech for DMC and DSMB activities, Tau Consortium for Scientific Advisory Board; grant funding through UCSD from Toyama Pharmaceuticals, AC Immune Biohaven Pharmaceuticals, and Vivoryon (Probiodrug); travel support from Toyama, Axon Neurosciences and Alion Pharmaceuticals and speaker fees to UCSD from World Events Forum, Optum Health, and Medscape, outside the submitted work. The remaining authors declare no conflicts of interest. Reprints: Mari L. DeMarco, PhD, DABCC, FCACB, Department of Pathology and Laboratory Medicine, St Paul’s Hospital, 1081 Burrard Street, Vancouver, BC, Canada V6Z 1Y6 (e-mail: [email protected]). Alzheimer Disease & Associated Disorders: October–December 2020 - Volume 34 - Issue 4 - p 357-359 doi: 10.1097/WAD.0000000000000372 Buy Metrics Abstract Cerebrospinal fluid (CSF) biomarkers amyloid-β and tau have been validated for the antemortem diagnosis of Alzheimer disease (AD) and are included in the AT(N) research framework for AD. Recently, an AT(N) CSF profile has been described for dementia with Lewy bodies (DLB), a disorder which is difficult to distinguish clinically from AD, particularly early in the disease course. Herein we describe a 71-year old male who presented with an atypical dementia syndrome including years of stability after an initial abrupt decline, marked visuospatial dysfunction, and relative sparing of memory. CSF biomarkers combined with the pattern of cognitive symptoms made AD unlikely and were consistent with DLB. This classification was confirmed clinically, with the emergence of classic DLB symptoms, and at postmortem pathologic examination. This case highlights the role for AD CSF biomarkers in facilitating earlier diagnosis of non-Alzheimer neurodegenerative dementias. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.