MMP9 and complex regional pain syndrome: The relative fold changes of HLA-A29.1, MMP9, ANPEP, HDC, G-CSF3R, and STAT3 in the CRPS group compared to the control group were 1.9±0.26, 4.0±1.23, 1.4±0.14, 1.8±0.27, 2.3±0.48, and 1.4±0.12 times, respectively (Fig. 3).