Reflex sympathetic dystrophy (RSD) syndrome (also called complex regional pain syndrome) is a chronic nerve disorder that occurs at the site of an injury, most often in the arms or legs. It often develops after injuries from high-velocity impacts such as those from bullets or shrapnel. However, it may occur without apparent injury.

RSD syndrome is unique in that it affects the nerves, skin, muscles, blood vessels, and bones at the same time. Symptoms include:

• Severe burning pain that is out of proportion to the severity of the injury and gets worse over time
• Pathological changes in bone and skin
• Excessive sweating
• Tissue swelling
• Extreme sensitivity to touch
• Warm, shiny red skin near the site of injury that later becomes cool and bluish