A participant who had apoE ε4 homozygosity treated with aducanumab developed severe ARIA-E with headaches, encephalopathy and alexia requiring treatment with corticosteroids (Filippi et al., 2022); while another participant homozygous with apoE ε4 treated with aducanumab had severe ARIA-E developing encephalopathy, epileptiform discharges, malignant hypertension and required corticosteroids (Vande Vrede et al., 2020). The gene discussed is APOE; the disease is Encephalopathy.