Given the current studies on Fibro....
Fibro is a central pain disorder. It occurs in the brain.
The new thoughts are that pain signals are amplified genetically in fibro patients. Like a radio turned up in volume that cannot be tuned down.

Fibro may be triggered by a peripheral event. This can be an injury, vaccine, arthritis etc.

New studies have found 8 times the incidence of fibro in relatives, suggesting a genetic weakness. Fibro does not cause swelling, discoloration, etc that is found in RSD patients.

But RSD may be a trigger for fibro in certain people.
At this time RSD is considered a neuropathic condition...a defect in the nervous system that affects the circulation to the affected area/site. So one person may have both. But some people may only have the RSD.

I am planning on attending a huge medical conference on chronic pain in late May. It is going to have a Fibro section. I went 2 yrs ago and it was amazingly informative!