However, the etiology of PD baffled physicians and scientists until 2 breakthrough discoveries: MPTP-induced parkinsonism in 1983 and the discovery in 1997 of the first genetic mutation in PD: SNCA. The recognition of α-synuclein being the major constituent of LB led to the hypothesis that α-synuclein spreads through different regions of the brain through six pathological stages of the disease [58]. The gene discussed is SNCA; the disease is Parkinson disease.