Many Fibro Patients Have Small-Fiber Polyneuropathy

Report from National Fibromyalgia & Chronic Pain Association

Small-Fiber Polyneuropathy (SFPN) is a disease with prominent widespread chronic pain and very similar symptoms as fibromyalgia. There are objective tests for SFPN, known causes, and the possibility of disease-modifying treatments and cure. Therefore, it is important that patients considered to have fibromyalgia be tested for SFPN, Anne Louise Oaklander, MD, PhD, associate in neurology at Massachusetts General Hospital and associate professor of neurology at Harvard Medical School in Boston, and colleagues reported at the American Neurological Association (ANA) 137th Annual Meeting.

BOSTON — In a small study of patients labeled as having fibromyalgia, almost half actually had small-fiber polyneuropathy (SFPN), a potentially treatable condition.

Therefore, it is important that patients considered to have fibromyalgia be tested for SFPN, Anne Louise Oaklander, MD, PhD, associate in neurology at Massachusetts General Hospital and associate professor of neurology at Harvard Medical School in Boston, and colleagues reported here at the American Neurological Association (ANA) 137th Annual Meeting.

"Fibromyalgia is such a common and expensive health care problem and although most people are aware of its existence now, it has no associated pathology with it," she explained. "So it's not a diagnosis in the true sense of the word, and that leaves patients frustrated and unable to gain real traction towards a cure."

Dr. Oaklander noted that despite an emphasis on central mechanisms as the cause of fibromyalgia, these findings suggest that a specific — and sometimes treatable — type of peripheral neuropathy is a common cause of the condition.

"This is exciting for us because it's the beginning of objective data on what the actual cause of patients' symptoms may be," she said.

Widespread Chronic Pain

The condition is a syndrome with prominent widespread chronic pain. Thus, her laboratory tested the hypothesis that some patients with fibromyalgia may have SFPN, which "produces widespread chronic pain and very similar symptoms. The difference though is that small-fiber polyneuropathy is a true disease, meaning that there are objective tests for it, known causes, and the possibility of disease-modifying treatments and cure," Dr. Oaklander told Medscape Medical News.

The investigators recruited 25 patients 18 years of age or older from the community who met the best available clinical and research definition of fibromyalgia (mean age, 46.5 years), as well as 29 control participants (mean age, 44.8 years). The groups were well matched for demographic characteristics, including sex (76% to 79% women).

The researchers applied consensus-recommended diagnostic tests for SFPN, including standard diagnostic autonomic function testing, an early neuropathy scale, and PGP9.5 immunohistochemical staining of a 3-mm skin punch biopsy specimen from the distal portion of the leg. PGP9.5 is a pan-axonal marker.

The diagnostic test results and markers were analyzed in a blinded fashion. Intraepidermal nerve fiber (IENF) densities were normalized to control values expected for age and sex.

"The diagnostic criterion, universally accepted around the world, is that someone whose nerve fiber density in their biopsy is below the fifth centile of predicted value is considered to have definite small-fiber polyneuropathy," Dr. Oaklander said.

"The major finding of our study is that half of the cohort of fibromyalgia patients but none of an age-matched control group had evidence of nerve loss. And so to neurologists this meets the diagnostic criteria for small-fiber polyneuropathy."

For the various tests overall, 46% of the patients with fibromyalgia and 17% of controls (P < .001) met the rigorous criteria for SFPN.

More specifically, 40% of the patients with fibromyalgia met the SFPN diagnostic criteria upon IENF staining. Their IENF densities averaged 28% ± 6% of the predicted norm vs 47% ± 6% for controls (P < .02).

Interestingly, there was no overall difference between patients with fibromyalgia and controls on autonomic function testing. Among the fibromyalgia cohort, 17% met diagnostic criteria for SFPN on autonomic testing vs 15% of controls (P = .67).

Link to Diabetes

"The significance of this finding is that unlike with fibromyalgia there are known causes of small-fiber polyneuropathy, many of which are amenable to treatment," Dr. Oaklander pointed out. "The most common 1 in the U.S. is diabetes, even prediabetes. So we're now moving on to test this cohort of patients for potentially treatable causes, which offer them the possibility of improvement and perhaps even cure."

In all of her studies, she said that when she found small-fiber polyneuropathy, "a substantial proportion of patients turn out to have either diabetes or pre-diabetes. Most of them don't even know that. It's so common.

"We noticed that virtually all of the patients that we were able to give an ultimate diagnosis of small-fiber [polyneuropathy] in fact said, 'Oh, I've been told I have fibromyalgia for the last 10 years'."

Besides diabetes, causes of SFPN include malignancies, autoimmune conditions, toxins, and mutations, and possible symptoms overlap those of fibromyalgia. Some patients with SFPN may not have pain but may have sensory loss or autonomic symptoms, such as abnormal blood pressure or gastrointestinal disturbances. Dr. Oaklander added that people at the lower end of the normal range of test results for SFPN may eventually develop symptoms.

Her laboratory and some other academic and commercial ones are accredited to run the IENF density tests.

Observing the poster, Gary Rosenberg, MD, professor and chair of the Department of Neurology at the University of New Mexico School of Medicine in Albuquerque, commented to Medscape Medical Newsthat he occasionally sees patients with fibromyalgia but noted, "They tend to go to the rheumatologist, not the neurologists" since fibromyalgia has traditionally been considered a rheumatologic condition. Dr. Rosenberg was not involved in the study.

Although fibromyalgia is purely a clinical diagnosis, this new information may add to the understanding of the pain syndrome "so it could be useful," he said, in that it explains the pathophysiology of some common pain presentations.

The study did not receive any commercial funding. Dr. Oaklander and Dr. Rosenberg have disclosed no relevant financial relationships.

American Neurological Association (ANA) 137th Annual Meeting in partnership with the Association of British Neurologists. Abstract W1409. Poster presented October 7-9, 2012.

article is here:

Here's some basic info on the subject at hand:

Small fiber neuropathy is a type of nerve damage that affects the tiny nerves under your skin that sense heat and cold, causing a number of uncomfortable symptoms.

  1. Causes

    • Possible causes of small fiber neuropathy include diabetes, HIV, genetics and drug or alcohol abuse, according to Phoenix Neurological Associates. In some cases, the cause of small fiber neuropathy symptoms is unknown.

    Types of Symptoms

    • Symptoms of small fiber neuropathy include reduced sensitivity to heat and coldness and severe pain. It is also possible to have a delayed or diminished reaction to pain caused by physical damage to the affected area, such as the feelings you experience when you step on something sharp.


    • The pain caused by small fiber neuropathy is described as burning, jabbing, stabbing and prickling, reports the Colorado Neurological Institute. Some patients experience a feeling that resembles an electric shock, while others describe the sensation as an intense pressure.


    • Small fiber neuropathy is most common in the feet, but it is also possible to experience symptoms in your legs or hands.


    • There is no cure for the symptoms of small fiber neuropathy. When the condition is caused by diabetes or substance abuse, reducing blood sugar or use of drugs and alcohol often improves symptoms, while in others antiseizure medications, narcotic pain relievers and antidepressants may alleviate pain.

Thanks Petunia, that adds perfectly to the other article. Simplifies things too. I guess I don't have it because I sure don't have diminished or delayed pain response. I have fast and intense pain reaction.

I have twice gone through these tests where they place objects like needles and nails into nerves and muscles and 'turn on the juice'. Funny these tests never even picked up on the severe Sciatica in my left leg. This procedure was absolute torture, you could have extracted any information out of me during this test, and I do not plan on EVER going through it again, it crashed me for weeks!

I have also refused a spinal tap, and will continue to.

I don't have slow or delayed reactions to pain either, and am just about finished with all invasive tests and treatments that simply make me worse!

Yes, I have always said that that the doctors always have to make you hurt even worse before they can help you. ....IF they can even help you. Often they can find the problem but it has no treatment.I'm like you. I even tell doctors that I won't go through painful tests, since none of them have ever helped me find a treatment for any condition.

I'm with you! I am having a series of tests next month because a lot of my symptoms don't all fit in with the Fibro diagnosis. I did refuse some of them because I don't feel they will serve any purpose except to make the doctors richer. I am hoping to see a Homeopathic doctor also since I don't respond well at all to medications. Just so darn tired of the mass of confusing symptoms.

Oh yeah, THAT test. Fun, isn't it - NOT. And obviously very effective as it didn't even pick up on your sciatica, SK.

Sheila, you're welcome. I didn't know anything about the ailment so had to look it up. Figured might as well share the info with you guys.

Doesn't sound like too many people with fibro will end up with this but what ho, if anyone here can find a better dx through this, good for them.

I hope a better diagnosis is awaiting you. Keep us posted, bookjunkie!

I see my rheumatologist in a few weeks. I will ask him about the possibilities of this for me. I saw a neurologist a couple of years ago for nerve testing because of cold, pain and numbness in my feet and we also ruled out MS with MRI. He did not mention anything about SFPN. I wonder who to see about SFPN?

Thanks for posting. Very interesting. Add another to the list of possibilities. Right? LOL!



I'm struggling because I feel whatever I have has progressed this winter. I was diagnosed with fms/cf, but I am coming to a place where I want answers again. I feel like it's futile, but I need help. Every day, if it's not one thing it's another. I used to use vicodin to get me through, now I am having weird side effects from that so there is no way to get over the really hard bumps in the road. I am suppose to drive to my daughters house next week (150 miles), which I have always done with no problem. How do I do this and spend the week in their home with the two small, beautiful grandkids? All of the activity and expectations of grandma are just expected and a given, right? Oh, I'm just feeling sorry for myself today.

You would see a neurologist L-Kitty. The test for this is very painful and the treatment is an anti-seizure medicine that also helps with nerve pain, but they make you very groggy. I often ask for the treatment before i get the test, and if the medicine helps, that's a pretty sure sign I have the problem. That way I avoid painful testing. You could ask your rheumie for a higher dose of pain meds, or there are natural things to help too. Vitamin B and D help with pain and central nervous system. I don't think the medical world has many answers about CF/FM. There are dozens of new diseases coming up every year that doctors don't know about and there are no tests or treatment I have been insulted and blamed by doctors who could not find the answers, so I am just dealing with things the best I can and looking for natural treatments.All doctors can do is pass out prescriptions, that for me, have worse side effects than the original illness, so I'm burned out on doctor's abuse in these difficult diseases.

Thank you, Sheila. No, I don't suppose I want to have any more testing done, not an invasive type anyway. I will keep my plan to see rheumy in a few weeks. It's been 3 years since I've seen him.

I do take a vitamin B-complex and D every day. You have a good idea with asking for treatment before testing. Although today is one of those badly fogged days, I googled a little bit and found out enough about the SFPN testing that I now know I want to avoid it...entirely.

Thanks again.


I really don''t know if anything I wrote made sense. LOL!

Yes L-Kitty,you made perfect sense. ;-)