My neurologist told me it is idiopathic and that about 12% of men over age 60 get it. He said that for unknown reasons soaking feet in epsom salts relieves symptoms, I tried it, and didn't work for me. Another doctor told me that there is a long list of possible causes, which is why that becomes an easy answer for med school students. After further discussions, I now believe that saying "idiopathic" is an easy way out of ordering extensive testing to rule out numerous possible causes. The good news is that small fiber neuropathy means some discomfort but not major disability, Although it is said to be progressive, I handle it like my other medical "gifts" ... with proper diet, the right exercise, good sleep, and minimizing stress. A positive mental attitude including a good dose of humor can be great medicine. I believe it is best to define ourselves by who we are as opposed to the ailments we have. Easier said than done, but it has worked for me.