Transgenic mice with deficient expression of the neuropeptides substance P (Tac1−/−) or CGRP (Ramp1−/−) show attenuated mechanical allodynia in the tibial fracture and casting model of CRPS.97 In addition, Ramp1−/− mice have reduced deposition of IgM in the skin, sciatic nerve, and spinal cord compared with wild-type animals 3 weeks after fracture.97 Thus, neuropeptide signaling may influence IgM autoantibody deposition after injury, and the antigenic targets of IgM may be localized to the skin and nerves. Here, CD40LG is linked to complex regional pain syndrome.