PSEN2 and Alzheimer disease: Clinically, AD is divided into ‘late-onset’ or ‘sporadic’ AD (LOAD)—which is the most common form of AD—and ‘early-onset’ or ‘familiar’ AD (EOAD), which accounts for 1-5% of all AD cases and is caused by dominantly inherited mutations in genes including APP, PSEN1, PSEN2, and APOE [6].