PSEN2 and early-onset autosomal dominant Alzheimer disease: Autosomal dominant (familial) Alzheimer's disease, due to mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2), or amyloid precursor protein (APP) genes, shares many features, both pathophysiologically and clinically, with the much more common sporadic form of the disease.6