The most significant side effect is Amyloid-Related Imaging Abnormalities (ARIA), which can appear as temporary brain swelling (ARIA-E) or small spots of bleeding (ARIA-H). While many cases of ARIA are asymptomatic and found only via MRI, in rare cases it may be fatal. Patients may experience headaches, confusion, dizziness, or nausea. Genetic testing for the ApoE4 gene is often recommended in the U.S. before starting treatment of an anti-amyloid therapy, as carriers have a several-fold higher risk of these complications.