CCL2 and complex regional pain syndrome: Previous studies on systemic biomarkers for CRPS have shown limitations in the specificity and utility of soluble cytokines such as TNF-α and IL-6.4,35,48 IL-1β,14 IL-2, and monocyte chemoattractant protein-12,34,48 have been previously reported as upregulated in patients with CRPS, and MCP-1 is known to play a role in mechanical allodynia in the spinal cord of TFM mice.16 Tumor necrosis factor-α, IL-6, and neuropeptide8 upregulation is reported in the TFM skin but has not been investigated in the serum.