I had the punch biopsies come up positive for SFN, and eveything else come up negative, in terms of etiology.

I did go thru autonomic testing, which since you have confirmed small fiber, might be worth doing to see if your autonomic system is affected. (Tilt table, thermoregulatory sweat, QSARTS, Valsalva and R-R breathing.) I had no idea I was so substantially affected in that area. It won't point to etiology, just to extent of involvement.

My neuro advised against a sural nerve biopsy, as he said the punch was plenty to confirm the SFN and he was concerned that it would leave me with residual problems.

We still do not have a handle on the etiology of SFN on me, as neither IVIG nor steroids stopped it (and I got a load of both and didn't want to continue due to side effects from steroids and not enough clinical data to support the treatment, he agreed.) I had no problems with IVIG.

I also have some central nervous system component going on.

Make sure they ruled out Celiac, (they probably have already).

You have a lot going on with several disease process, altho ankylosing spondylitis is related to Crohn's, they haven't made the connection yet to SFN and AS...You are definitely a case that should be followed by a research facility, because your case can be one of those ground breakers in terms of linking one disease to another. Although your top priority should be your own health, your case could also help others.

With Crohns, good nutrition is going to be essential, but you know that already. With AS on top of SFN pain control will be one of your challenges.

You sound like you have a good handle on your health care management and have made very good decisions thus far. Hang in there.