Are you able to move around or do any activity? I am not familiar exactly but I remember my rsd pain doctor saying that if I did not move more he thought I was going to atrophy. Now I know it is hard when the pain is so high but a thought that came to mind. I hope you feel better

--that muscle wasting would be involved in a predominantly small-fiber neuropathy, as the small fibers subsume the sensations of pain and temperature and do not ennervate muscle.

If there is muscle wasting as well that implies there is also large fiber involvement of some sort. Large, myelinated fibers include all motor neurons as well as those that involve the sensations of mechanical touch, vibration, and positioning in space.

Of course, one can get some degree of muscle wasting just from lack of exercise, which happens to a lot of people with debilitating conditions. The trick is to see if it related to the condition itself as opposed to a secondary effect.

I have muscle wasting but it is due to the large fiber neuropathy, hereditary. I have not heard of it being related to SFN. I have SFN as well. Have you had an EMG/NCS ? Have they ruled out large fiber?
Also if it is due to the neuropathy it is usually a slow process. What is happening to you sounds very scary. Is there any genetic history of something like this in your family? When you say full body, I take it you do not mean just arms and legs which is the usual progression. How far does your numbness extend?