Adjusted models showed that the anti-inflammatory marker, fractalkine, was significantly decreased in PD-NoFOG and PD-FOG groups compared to HC (≈23%, F1,37 = 12.6, P = 0.002, adjusted for sex and duration), and further decreased in PD-FOG compared to PD-NoFOG (≈24%, F1,27 = 8.7, P = 0.007). This evidence concerns the gene CX3CL1 and Parkinson disease.