Reflex Sympathetic Dystrophy.
It's thought to result from damage to the nervous system, including the nerves that control the blood vessels and sweat glands.
The damaged nerves are no longer able to properly control blood flow, feeling (sensation), and temperature to the affected area. This leads to medical problems in the Blood vessels, Bones, Muscles, Nerves and Skin.
Symptoms include burning, shooting pains, muscle spasms, temp. changes (ie, cold hands), numbness and tingling in extremities, shoulders and neck.
Mine showed up after my Left Ulner Nerve got crushed when I fractured my wrist.
Can't find any conclusive articles that tie it to autoimmune disease. But, I do wonder if that didn't play a role in my susceptability.