EDN1 and neuropathy, small fiber: A systematic review of 11 original studies involving 299 CRPS Type I patients identified several potential skin biomarkers linked to underlying pathophysiological processes, including inflammation (via interleukins and TNF-α), vascular dysregulation (ET-1/NOx imbalance and hypoxia-related lactate elevation), small-fiber neuropathy, and hypersensitivity.