PSEN2 and Alzheimer disease: Early-onset AD (EOAD) is usually autosomal dominant inherited, constituting barely 1–2% of AD, with genes including amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) being regarded as major factors (Reitz et al., 2011; Alzheimer’s Association, 2015).