It is characterized by specific genetic alterations, including mutations in genes such as presenilin 1 (PSEN1) located on chromosome 14q24.2, which is identified in up to 70% of familial AD cases, presenilin 2 (PSEN2) on chromosome 1q42.13, and the APP gene on chromosome 21q21.3. This evidence concerns the gene PSEN2 and Alzheimer disease.