I understand, but my experience was different. I had four neurologists tell me that at least 30% of skin punch biopsies are negative…despite patients still having symptoms. Maybe that’s the same percentage with idiopathic SFN, which is a huge number. My main neurologist told me this is why someone would say, “It won’t necessarily change the treatment.”

It’s important to find a cause, if one is findable, and the skin punch biopsy can help point to a cause, but in a lot of cases it does not. And even if one does find a cause, the treatment may be the same, i.e. it’s common with fibromyalgia but there’s no direct treatment for fibromyalgia, just symptoms management.

Mine was inconclusive (one sample was “low normal” and the others were not a good sample; I can’t remember exactly, but it wasn’t worth doing again), I have no history of diabetes, a normal glucose tolerance test, no exposure to a chemical, nor B12 deficiency, chemotherapy, never took any medications regularly until that point, etc. It was obvious it was length-dependent because in the time I waited for an appointment, the symptoms began in my feet and crept up higher. All of that was apparent before the skin punch biopsy.

I still decided to do it because I wanted certainty about whether I did or did not have small fiber neuropathy and not some other more resolvable condition. Sadly it didn’t give me that.

My small fiber neuropathy is assumed to be autoimmune because I have an assumed diagnosis of a seronegative inflammatory arthritis (no objective biomarker and joint damage would may not be apparent for decades without treatment despite severe pain) and an objective diagnosis of POTS, which affects the autonomic nervous system—which also relies on small fiber nerves. Treating the inflammatory arthritis improved the joint pain, but not the SFN. IVIG would be my “hail Mary” pass but it’s a toss-up.