Sorry for your diagnosis,CG.

I am SFN only. I have a very good neuro, and I had similar fears as you did. Mine also started acutely and was full body. The course is really different for everyone. I have a lot of twitching and some cramping, but no actual large fiber or motor involvement. My neuro says twitching and cramping can be very common with SFN. The twitching and cramping fluctuates, just like all of my other SFN symptoms.

My neuro also made it clear that it is pretty uncommon for neuropathies that start off as small fiber sensory to progress to motor neuropathies...so just echoing was Glenn has said.

I was very overwhelmed and terrified when I was diagnosed. I too was hoping I was just wacky in the head, so when the doctor told me my biopsies at thi and ankle were both positive, I was very distraught. My anxiety went through the roof, and along with it so did my pain. I have come to terms with the fact that for me, stress and anxiety WILL increase my pain and symptoms, so I try to be proactive and optimistic (not always possible of course haha).