A CPA aged 69 years in relatively good health except for mild type 2 diabetes (hemoglobin [Hb]A1c = 6.6%) treated with metformin presented with increasing dyscalculia for the past 8 months together with problems remembering clients' financial issues and brief, intermittent uncharacteristic explosive episodes of hypomania, all of which had adversely affected his professional performance. His family urged him to have a neurologic evaluation, including a neuropsychologic test battery and a brain MRI, after which he was diagnosed with mild cognitive impairment. Because of his long-standing intention not to retire, his family encouraged him to begin treatment with an anti-amyloid beta monoclonal antibody (anti-Aβ mAb). After 18 months of treatment, his mild cognitive impairment had not progressed, but a routine surveillance brain MRI revealed a single focus of left temporal lobe parenchymal edema 5 to 10 cm in diameter with sulcal effacement compatible with moderate amyloid-related imaging abnormalities (ARIA)-E without any associated symptoms. It was decided to continue treatment, and a follow-up brain MRI 1 month later showed no resolution of ARIA-E together with a hyperintensity less than 5 cm in diameter in another brain region compatible with ARIA-E. The patient continued to show no clinical evidence of ARIA.