This could explain why patients with CRPS experience abnormal pain after a relatively minor injury. It also suggests that the injury does not cause the intense pain. The pain comes from the way the body has responded to it.
The SNS also regulates the blood vessels of the skin, so that a malfunction could lead to changes in skin color and temperature, one of the signs of CRPS.
Some cases of CRPS, however, show no evidence of SNS malfunction.
Immune system malfunction theory
Another theory is that Type 2 CRPS is linked with problem with the immune system.
When an injury occurs, the affected part may swell, as the immune system tries to stop the trigger that started this response.
Studies have shown that people with CRPS have raised levels of inflammatory chemicals, or cytokines, in their tissues.
Some experts suggest that inflammation continues after the injury has healed, irritating the nerves in that area and causing pain, redness, swelling, and warmth.
People with other inflammatory and autoimmune disorders such as asthma are more likely to have CRPS.