RSD or CRPS is a chronic pain disorder. It involves the sympathetic nervous system and is ordinarily the result of an injury or trauma. It could also be caused due to after affects of surgery, or myocardial infections. 

RSD in its serious form is known as the Complex Regional Pain Syndrome  it is so called because ordinarily the disease will start at one place very near to the place of injury. The intensity at first may be mild or barely noticeable. But as the days pass by the intensity will grow and the disease may spread to other parts of the body. Most of the patients would complain about acute pain coupled with burning sensations in various parts of the body. As the time passes and if treatment is not doled out, the disease grows more intense and complicated and becomes even more painful.  

A lot of RSD Medical Information is available in the market as well as online. But till date RSD continues to be a poorly understood complex disease. Though your hand and foot are the most affected areas, other parts of the body could also be affected. Till date however, doctors are unable to say why hand and foot are singled out for attack and why other parts of the body are not spared.