Brief ReportsCerebral Amyloid Angiopathy-related Inflammation Presenting With a Cystic Lesion in Young-onset Alzheimer DiseaseRingman, John M. MD, MS*; Joe, Elizabeth MD*; Sheikh-Bahaei, Nasim MD, PhD*,†; Miller, Carol MD*,‡; Vinters, Harry V. MD§; Guzman, Samuel MD‡; Chui, Helena C. MD*Author Information *Department of Neurology, Memory and Aging Center, Keck School of Medicine †Department of Radiology, University of Southern California ‡Department of Pathology, Keck School of Medicine at USC §Department of Pathology and Lab Medicine (Neuropathology), and Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA This study was supported by NIH U01 AG051218 and P50 AG005142. The authors declare no conflicts of interest. Reprints: John M. Ringman, MD, MS, Helene and Lou Galen Professor of Clinical Neurology, Department of Neurology Keck School of Medicine at USC Center for Health Professions 1540 Alcazar Street, Suite 210 G, Los Angeles, CA 90033 (e-mail: [email protected]). Alzheimer Disease & Associated Disorders: July-September 2021 - Volume 35 - Issue 3 - p 265-268 doi: 10.1097/WAD.0000000000000432 Buy Metrics Abstract We describe a patient with cerebral amyloid angiopathy-related inflammation (CAA-ri) presenting as Alzheimer disease (AD) with a mass lesion with symptom onset at age 59. He was found to have a nonenhancing lesion in the right temporal lobe on magnetic resonance imaging without evidence of hemorrhage. He underwent a biopsy which showed amyloid beta in blood vessel walls and a perivascular inflammatory infiltrate consistent with CAA-ri. Neurofibrillary tangles were present and a flortaucipir positron emission tomography showed bilateral signal highest in the lateral temporal and parietal cortices. A lumbar puncture showed tau, p-tau, and amyloid beta levels consistent with AD without evidence of inflammation. He was homozygous for the APOE ε4 allele. He died at age 67. A focus of CAA-ri can be present in the context of AD with a mass lesion and without evidence of hemorrhage, significant ischemic changes, or overt inflammation on cerebrospinal fluid examination. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.