--given that you do seem to have some autoimmune issues, there definitely needs to be other autoimmune testing, if you have not had it (Mass General is usually pretty good about this; it's more conversant in neuropathic syndromes than many others).

I'm not only speaking of the rheumatological testing, though many ANA related conditions can cause a sensory or sensorimotor neuropathy through various mechanisms, but testing for antibodies to nerve, as well. (When one has one autoimmune situation, there are likely to be other as well.)

This paper helps to delineate some of those tests:

http://www.questdiagnostics.com/hcp/...eralNeurop.htm

Also, did the GI testing include a good look for the flattened villi of celiac, an often overlooked cause of neuropathy?