For autosomal dominant early-onset Alzheimer's disease (EOAD), mutations in the APP, presenilin 1 (PSEN1), or presenilin 2 (PSEN2) gene sequence are a major risk factor, while the APOE4 allele is a major risk factor for late-onset Alzheimer's disease (LOAD) [82]. The gene discussed is PSEN1; the disease is Alzheimer disease.