IL6 and complex regional pain syndrome: Inflammatory cytokine levels are up-regulated in CRPS skin [23-25], and levels of interleukin 1b (IL-1b), interleukin 6 (IL-6), tumor necrosis factor a (TNFa), and nerve growth factor (NGF) are elevated in the hindpaw skin keratinocytes of fracture rats [16,26-28].