Reflex sympathetic dystrophy also called Complex regional pain syndrome (CRPS) is a chronic pain condition. The key symptom of CRPS is continuous, intense pain out of proportion to the severity of the injury, which gets worse rather than better over time. CRPS most often affects one of the arms, legs, hands, or feet. Often the pain spreads to include the entire arm or leg. Typical features include dramatic changes in the color and temperature of the skin over the affected limb or body part, accompanied by intense burning pain, skin sensitivity, sweating, and swelling. Doctors aren’t sure what causes CRPS. In some cases the sympathetic nervous system plays an important role in sustaining the pain. Another theory is that CRPS is caused by a triggering of the immune response, which leads to the characteristic inflammatory symptoms of redness, warmth, and swelling in the affected area. Because there is no cure for CRPS, treatment is aimed at relieving painful symptoms. The prognosis for CRPS varies from person to person. Spontaneous remission from symptoms occurs in certain individuals. Others can have unremitting pain and crippling, irreversible changes in spite of treatment.