There are two major types of complex regional pain syndrome (CRPS):

• Type I. Previously known as reflex sympathetic dystrophy syndrome, it is the result of an illness or injury to the skin, joints, bones or other tissues of an affected area but can develop even without a known injury.
  
  
• Type II. Previously known as causalgia, it occurs after an injury to a major nerve.

When these forms of CRPS are left untreated, they may progress to more dangerous forms of CRPS. For example:

• Symptoms migrate from the initial site of the pain (such as the hand or foot) to the shoulder, trunk and face. Such symptoms can affect an entire quadrant of the body.
  
  
• Symptoms may spread from one limb to the opposite limb.
  
  
• Symptoms may leap to a distant part of the body.