My first thought as someone who has high comorbidity of autoimmune diseases is that this sounds like extremely severe neuropathic pain.
Since I wasn't familiar with CRPS I did a quick search for it and found this article
http://www.ninds.nih.gov/disorders/reflex_sympathetic_dystro...
A search for autoimmune on that page turns up this nugget,
"CRPS is more common in individuals with other inflammatory and autoimmune conditions such as asthma." Seeing as how it is a rare disease very little research is going to go towards this, so I'm just throwing out some conjecture that CRPS is likely an autoimmune disease itself.
Autoimmune diseases often cause neuropathic pain. Link below provides some details, a quick excerpt though is provided here.
"Neuropathic pain is distinguished from other pain conditions where the pain generator begins with disease of nonneural tissues. These nonneuropathic pain entities are said to be nociceptive and include conditions such as osteoarthitis and inflammatory pain."
Now to put it in layman's terms from a patient that doesn't understand the medical condition (me); the pain comes from my nerves/brain not working right.
I'm nowhere near as bad as the guy in this article; I am highly functioning on a day to day basis, but still have to use benzodiazepines in conjunction with opiates. As I understand it the former helps to slow down the overreaction of messages going between the nerves and brain, while the latter helps to take the "edge" off from the constant pain that remains.
The pain can come from anywhere and everywhere. I really feel for this guy; on a real bad day the pain has gotten so bad I can barely get out of bed and move. On the rare occasion that happens I double up on the drugs and sleep it off. Sounds like this guy is suffering times 1000 on a daily basis what I am on my worst days. That's some seriously awful shit.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1810425/