In cold CRPS patients, an imbalance between the vasodilator NO and the vasoconstrictor endothelin-1 (ET-1) in artificial blisters on the skin of the affected extremity has been demonstrated (Groeneweg et al., 2006); evidence that advised about the role of endothelial dysfunction linked to aberrant inflammatory responses in CRPS vasomotor disturbances (Groeneweg et al., 2008, 2009). Here, EDN1 is linked to endothelial dysfunction.