The mean plasma α-synuclein and β-synuclein levels in the autism group were 12.04 ± 7.35 ng/mL (95% CI 9.01–15.07) and 1358.22 ± 173.14 ng/mL (95% CI 1286.75–1429.69), respectively, and 8.65 ± 3.80 ng/mL (95% CI 6.45–10.85) and 1319.14 ± 136.67 ng/mL (95% CI 1240.33–1398.05), respectively, in the PDD-NOS group. This evidence concerns the gene SNCB and pervasive developmental disorder - not otherwise specified.