I was actually diagnosed with Small Fiber Neuropathy about 5 months ago via skin punch. It is considered idiopathic. They have ruled out diabetes as I have passed all blood three tests for it on more than one occasion. I have a large thyroid nodule and a few small ones (benign). My thyroid levels are considered normal even though the THYROID PEROXIDASE (TPO) AB is high (43). every other possible blood test has been done, vitamins, toxins, etc. They have given up sent me off and said lets see if something comes up later. But small fiber neuropathy is very painful.