We investigated whether the selected polymorphisms were associated with Hcy levels in PD and found an association between the MTHFR rs1801133 TT genotype and increased Hcy levels in PD after correction for multiple testing (TT vs. CC: β = 3.79; 95% CI 1.76–5.82; corrected P = 0.026) (Table 2). The gene discussed is MTHFR; the disease is Parkinson disease.