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). This evidence concerns the gene SNCA and Alzheimer disease.