The first evidence of α‐synuclein involvement in PD came from several familial studies that showed individuals harboring coding region mutations in SNCA, and the gene encoding α‐synuclein, including A53T, E46K, and A30P, had early‐onset disease with an autosomal dominant pattern of inheritance (Polymeropoulos et al, 1997; Kruger et al, 1999; Zarranz et al, 2004). This evidence concerns the gene SNCA and Parkinson disease.