Hello, it is me that is being treated for Erythromelalgia right now! There is no test for this condition. It is diagnosed by symptoms, appearance (red skin), and warmth to the touch. However everybody presents differently. Right now I have no burning sensation yet but everything from my knees down are very swollen and red. I've had chronic swelling for years that comes and goes every summer and sever pain on tops of feet for a couple years.
Just thought I'd share my experience in case it rings any bells with you. oh, and it can affect Limbs (typically feet and/or hands but can affect entire limbs) and face as well I read.
Anyway I'm assuming you've been to a foot dr and have had MRI's?
Does your pain move all around your body? I have Fibro as well. Had chronic pain for 24 years. drs always blamed my spine. until JUST 2 weeks ago when I flared and the EM flared as well. I understand you frustration. There IS a blood test for Fibro. It's not covered by insurance though. You can ask your neurologist for it. I don't know if it's new or what but I was NEVER told of this test.
I hope maybe some of this helped! Good luck!