PSEN2 and Alzheimer disease: For example, early-onset AD (EOAD), constituting barely 1–2% of all cases of AD and being diagnosed before the age of 65 years, is usually autosomal dominant inherited with genes including APP [9], FKBP1B [10], PSEN1 [11,12] and PSEN2 [11,12] being regarded as major factors.