Complex regional pain syndrome (CRPS) type 1, also known as reflex sympathetic dystrophy, is a chronic pain condition characterized by severe, continuous pain in a limb, usually following an injury or trauma. The pain is disproportionate to the initial injury and may be accompanied by swelling, skin color and temperature changes, and abnormal sweating. The exact cause of CRPS type 1 is not well understood, but it is believed to involve abnormal functioning of the nervous system.