MMP9 and complex regional pain syndrome type 2: Based on previous studies and our results, we could assume that the direction of regulation of HLA-A29.1, MMP9, and HDC genes may be the same in both CRPS I and CRPS II, although the level of regulation in CRPS II was greater than that of CRPS I, that the up-regulation of IL8 and the down-regulation of ARHGEF10 gene may be related with the pain progression of CRPS I, and that the up-regulation of ANPEP, G-CSF3R, and STAT3 genes may be associated with the pathogenesis of CRPS II.