PSEN2 and early-onset autosomal dominant Alzheimer disease: While most of the Alzheimer’s disease (AD) cases are sporadic and manifest after age 65 (late-onset AD, LOAD), a subset of patients develop symptoms earlier in life (early-onset, EOAD) due to mutations in the PSEN1, PSEN2, or APP genes with an autosomal-dominant inheritance pattern (AD-EOAD).