An early-onset (average ∼45 years) genetically driven dominantly inherited familial form, where the increased Aβ production is due to mutations in its precursor, amyloid precursor protein (APP), or APP cleaving presenilin 1 or 2 (PSEN1, PSEN2), accounts for less than 1% of the AD cases (1, 2, 3, 4). The gene discussed is PSEN1; the disease is Alzheimer disease.