<h4>Objective</h4>This study investigates the independent and interactive effects of apolipoprotein E (APOE) genotypes and white matter hyperintensities (WMH) on distinct neuropsychiatric symptom (NPS) phenotypes in patients with Alzheimer's disease (AD).<h4>Methods</h4>We enrolled 325 AD patients consecutively diagnosed at a specialized memory clinic between May 2024 and May 2025. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.