Lower mean concentrations of CSF t-α-syn were observed in patients with sPD (mean ± SEM = 22.81 ± 4.198 ng/ml, n = 35), LRRK2-PD (mean ± SEM = 20.54 ± 3.139 ng/ml, n = 13), and LRRK2-H (mean ± SEM = 17.84 ± 2.569 ng/ml, n = 20) than in age-matched controls (mean ± SEM = 24.74 ± 4.470 ng/ml, n = 42) (P = 0.7001, Mann-Whitney U-test). This evidence concerns the gene LRRK2 and Parkinson disease.