What causes Fibro? 
They think its a genetic marker that sometimes is set off by trauma or illness. 
Trauma is the trigger
There are 3 major theories that I can find about what Fibro is: 
1) Inflammation
2) too many nerves in the hands and feet firing pain signals
3) brain damage (too much blood flow in pain receptors, too little flow in pain stoppers and as a bonus the cover of the brain is deteriorated so that causes fog and fatigue.
They know these 3 things happen, but no idea which if any are the cause and which are the results.
Or door #4 and none are the cause and all are the symptoms of something they haven't found yet.