The name of Pain may be CRPS, but it doesn't automatically mean that any and all other unexplained pain would always be CRPS too. Logically, we could reason it as follows:
a) CRPS can spread beyond the original site in some people; (true)
b) I have CRPS in my arm and new Pain in my legs - my Pain has spread beyond the original site;
THEREFORE - These new Pain symptoms in my legs must be CRPS (logically true but it is based on the assumption that there are no other causes to Pain)
It is an easy assumption to make, but to rely on this assumption would be dangerous without evidence. What if there was a life-threatening problem that ends up ignored because it mimics symptoms of a condition you have already? You can see the danger. It's such an easy one that even I made it. Granted, it felt very similar. This new Pain was largely untouched by pain medication. I slept without covers on my legs because it was too painful, and showers were becoming more uncomfortable - and dangerous until I got a shower stool. I started wearing lots of skirts and stockings instead of my usual jeans, and was thankful that it was coming into summertime. I wished I could go barefoot in public without fear of stepping in glass, dog shit or being impaled through the foot with a stiletto! Being touched was enough to send me through the roof, and my usually sparsely-haired legs took on a more hirsute hippie vibe. This was rather annoying, especially with the very pale skin tone (I never had much colour variation, not being fully caucasian I don't even turn a proper red when sunburnt), it stood out even more. I couldn't do a sugar wax or even run a razor over my hypersensitive skin. Yes, Pain and disability, and yet we still have time to be vain! Actually, it's not all about vanity. I discovered with my arms years ago the exact reason we as a species used to be more hairy - because each one of those hairs can pick up and read sensation from our environment. Each hair follicle could pick up minute changes in the same way as cats' whiskers, or the way insects detect movement close by. For me, each one of those hairs were made of tiny fire ants, biting the living blazes out of my legs while they were crushing them to a pulp from every dimensions!
It sure felt like CRPS!