Severe symptomatic amyloid-related imaging abnormalities in Alzheimer's disease: Two case reports and systematic review of reported cases

BackgroundAmyloid-related imaging abnormalities (ARIA) are a recognized complication of anti-amyloid monoclonal antibodies for Alzheimer's disease (AD). While typically asymptomatic, a subset of patients develops severe clinical symptoms and radiological findings requiring intensive management. Data on their presentation, treatment, and outcomes remain limited.ObjectiveWe report two cases and analyze the clinical features of all published cases of severe symptomatic ARIA, with a focus on associated risk factors, therapeutic approaches, and patient outcomes.MethodsWe report two cases of severe symptomatic ARIA in patients treated with gantenerumab. A systematic review was conducted following PRISMA guidelines using MEDLINE, Web of Science, and manual reference screening. We included case reports and series providing individual-level data on symptomatic ARIA episodes classified as severe by clinical criteria. Demographic, genetic, clinical, radiological, therapeutic, and outcome data were extracted.ResultsThirty-six cases were included (2 new and 34 from 21 publications). Fifteen cases were associated with lecanemab, 10 with gantenerumab, 6 with donanemab, and 5 with other antibodies. <i>APOE</i> ε4 was present in 62.5%, including 10 ε4/ε4 homozygotes. Baseline MRI showed hemorrhagic markers in 10 cases, including superficial siderosis in 2 of the 5 patients with isolated macrohemorrhages. Most episodes occurred within 6 months of treatment. Symptoms included altered consciousness (75%), focal deficits (66.7%), seizures (38.9%), and headache (36.1%). ARIA-E resolved in all non-fatal cases. Corticosteroids were used in 72%. Among the patients whose outcome data were available, 15 patients recovered completely, 10 had persistent deficits, and 10 died.ConclusionsSevere symptomatic ARIA is a rare but serious adverse effect of anti-amyloid therapy. Standardized diagnostic and therapeutic guidelines are needed to minimize ARIA-related morbidity and mortality.PROSPERO registration no. CRD420251055067.