The mechanism(s) underlying the appearance of the α-syn inclusions could be related to an overexpression due to some genetic defect or/and a malfunction in its protein breakdown system and misfolding and accumulation of α-syn may be linked to some defect in its gene, SNCA. In 1997, the first pathogenic SNCA mutation was reported in PD families (Polymeropoulos et al. 1997). The gene discussed is SNCA; the disease is Parkinson disease.