IL2 and Parkinson disease: This analysis showed a significant association between PD-CRS total score and vitamin B12 values (β = 0.169; p < 0.05), homocysteine levels (β = − 0.194; p < 0.05) and iron levels (β = 0.177; p < 0.05), and a specific mild association between PD-CRS posterior-cortical performance and IL2 values (β = − 0.269; p < 0.005).