Three of the most common neurodegenerative diseases are Alzheimer’s disease (AD), characterized by Aβ plaques and tau tangles, the primary tauopathies, [frontotemporal dementia with tau pathology (FTD), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD)] characterized by tangle pathology and Parkinson’s disease(s) (PD), usually characterized by synuclein Lewy bodies. The gene discussed is SNCA; the disease is Alzheimer disease.