These proteins include α-synuclein (α-syn) inclusions found in Lewy bodies and Lewy neurites in Parkinson disease (PD) and Parkinson disease dementia (PDD), extracellular amyloid-β (Aβ) plaques and phosphorylated-tau (tau) inclusions in the form of intracellular neurofibrillary tangles in Alzheimer’s disease (AD) (Goedert, 1993, Joachim and Selkoe, 1989, Spillantini et al., 1997). The gene discussed is SNCA; the disease is Parkinson disease.