The histopathology of PD is also characterized by the presence in neurons of Lewy bodies, which are composed mainly of aggregates of the α-synuclein (α-Syn) protein (see Box 1 for a glossary of terms) (Lewy, 1912; Spillantini et al., 1998; Shults, 2006). This evidence concerns the gene SNCA and Parkinson disease.