I believe that RSD is called a "neuropathy"... This means a disorder of a nerve(s).

But RSD is different, as it is more severe, and when spread, more severe. RSD appears to favor the sympathetic nerves. Most peripheral neuropathies are sensory at first, with the more severe type, affecting motor functions (autoimmune), or genetic spreading. Most PNs have numbness. Peripheral neuropathies don't always follow a trauma or injury like RSD does. Peripheral neuropathies may be induced by poisons (pesticides, arsenic) or drugs. PN may occur in diabetics as a complication.

There are many kinds of PN, most do not swell or discolor however.

RSD and PN share dysautomnia symptoms, and gastroparesis however.

I think it is important for RSDers to make sure they don't have PN as an overlap, as PN sometimes responds to Vit D and B12.
Also some respond to carnitine, and other nutrients like lipoic acid. People can have more than one illness/syndrome, and keeping an open mind when new symptoms crop up may be to your advantage.