ARIA-E After Donanemab in an APOE ε4 Carrier: Risk Stratification, Management, and Rechallenge Considerations
Brian Paquette, DO, MPH — ApoE4 Insights | Clinical Pro
Case Presentation
A 77-year-old woman with APOE E3/E4 genotype, mild dementia (Alzheimer's disease), and hypercholesterolemia — otherwise medically fit — is receiving donanemab (Kisunla) for early symptomatic AD. She completed her 6th infusion one month ago. A pre-infusion brain MRI (obtained in anticipation of the 7th dose) demonstrates bilateral parietal FLAIR hyperintensity consistent with ARIA-E. She is clinically asymptomatic.
1. Radiographic Classification: Why Bilateral ARIA-E Is Clinically Significant
ARIA-E severity is graded by FLAIR imaging characteristics per the FDA-approved Kisunla prescribing information:
| Grade | FLAIR Criteria | Default Action |
|---|---|---|
| Mild | Single site <5 cm | May continue dosing |
| Moderate | Single site 5–10 cm, OR multiple sites each <10 cm | Suspend until radiographic resolution |
| Severe | Any site >10 cm | Suspend; consider permanent discontinuation |
Clinical implication for this patient: Bilateral parietal involvement, by definition, represents multiple FLAIR sites — classifying this case as at least moderate ARIA-E. Precise measurement of each lesion on FLAIR by neuroradiology is required to determine whether any individual site exceeds 10 cm, which would reclassify as severe.
The ACR Appropriateness Criteria for Dementia (2024) specifies that mandatory MRI sequences for ARIA detection include DWI, T2 FLAIR, and T2 GRE or SWI. The differential diagnosis for ARIA-E on imaging includes CAA-related inflammation, posterior reversible encephalopathy syndrome (PRES), progressive multifocal leukoencephalopathy, subacute infarcts, meningitis, and vasculitis — all of which warrant clinical consideration before attributing findings solely to donanemab.
2. APOE ε4 and ARIA-E Risk: What the Trial Data Show
APOE ε4 carrier status is the most clinically relevant genetic risk modifier for ARIA-E. In the TRAILBLAZER-ALZ and TRAILBLAZER-ALZ 2 trials, ARIA-E rates were substantially higher in ε4 carriers:
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