For those of you who don't know, Causalgia (CRPS/RSD) should rank high on the list of 'Things-You-Don't-Want'.
On the IASP definition:
A syndrome of sustained burning pain, allodynia, and hyperpathia after a traumatic nerve lesion, often combined with vasomotor and sudomotor dysfunction and later trophic changes.
Or as it was first described by Silas Weir Mitchell in 1872 after the Civil War
"We have some doubt as to whether this form of pain ever originates at the moment of the wounding. . . Of the special cause which provokes it, we know nothing, except that it has sometimes followed the transfer of pathological changes from a wounded nerve to unwounded nerves, and has then been felt in their distribution, so that we do not need a direct wound to bring it about. The seat of the burning pain is very various; but it never attacks the trunk, rarely the arm or thigh, and not often the forearm or leg. Its favorite site is the foot or hand. . . Its intensity varies from the most trivial burning to a state of torture, which can hardly be credited, but reacts on the whole economy, until the general health is seriously affected....The part itself is not alone subject to an intense burning sensation, but becomes exquisitely hyperanesthetic, so that a touch or tap of the finger increases the pain." quoted in UCLA pain exhibit
In other words, in causalgia part of your body feels like it's constantly on fire.