I have small fiber neuropathy diagnosed by skin biopsy. i have the neuropathy in both legs, both arms, and head. i dont have diabetes or vitamin deficiencies. would this widespread small fiber neuropathy most likely be caused by an autoimmune issue?

It could be but you need a careful evaluation by a immunologist to determine that. good luck

There are now several known possibilities, with the most common being diabetes and pre-diabetes. Genetic disorders and autoimmune problems need testing to confirm. Sometimes, answers are elusive, and may not be uncovered for a few years. An experienced neurologist can track this down if the standard protocols are followed.