We also observed that the expression level of HLA-A29.1, MMP9, ANPEP, HDC, G-CSF3R, and STAT3 significantly differed in the CRPS II patients, when compared to that in the controls (p = 0.020, 3.4×10−7, 3.0×10−5, 0.020, 3.0×10−5, and 3.0×10−5, respectively). Here, MMP9 is linked to complex regional pain syndrome type 2.