Notably, dominantly inherited mutations both in the presenilins and in APP are currently the only known causes of the familial form of AD (FAD), which has led to the most widely accepted hypothesis to explain the pathogenesis of AD, namely, the “amyloid cascade,” which proposes that deposition of Aβ in the brain is the precipitating pathological event in AD3. The gene discussed is APP; the disease is Alzheimer disease.