By Donna Gregory Burch.
We’ve all been told fibromyalgia is a diagnosis of exclusion, but how thorough was your doctor in ruling out other conditions that mimic fibromyalgia? I’m sure we were all tested for rheumatoid arthritis, lupus, hypothyroidism, anemia and maybe Lyme disease, if we were lucky.
But I bet there’s one test most of our doctors skipped: a skin biopsy for small-fiber polyneuropathy (SFPN). SFPN is a neurological condition that causes chronic widespread pain and affects autonomic functions in the body, such as heart rate, blood pressure and sweating.
Multiple studies have confirmed SFPN is extremely common in fibromyalgia patients.
But Anne Louise Oaklander, associate professor of neurology at Harvard Medical School and director of Massachusetts General Hospital’s Nerve Unit, doesn’t think SFPN is just a comorbidity of fibromyalgia; her research suggests SFPN may actually be the cause of fibromyalgia in some patients.
In 2013, Oaklander published a study that found 41 percent of fibromyalgia patients tested positive for SFPN using a skin biopsy versus only 3 percent of healthy controls. Fibromyalgia patients with SFPN were then tested for various causes of the neurological condition, and Oaklander found an interesting trend: The most common cause of SFPN found among patients with fibromyalgia was immune system dysfunction.
These findings could be a game changer for some fibromyalgia patients since SFPN can be treated, and in some cases, cured.
“This provides some of the first objective evidence of a mechanism behind some cases of fibromyalgia,” Oaklander said in a press release. “Identifying an underlying cause is the first step towards finding better treatments.”
Oaklander says many physicians - even some neurologists - have not heard of SFPN, so that’s likely why so many of us with fibromyalgia were never screened for it.
SFPN can cause a range of symptoms reported by fibromyalgia patients, including various manifestations of pain, chronic fatigue, digestive issues, brain fog, headaches and many others.
“A lot of these fibro patients I’ve seen may have gone to see dozens of different doctors over the years,” Oaklander said during an interview. “What happens is [medical providers] haven’t focused on finding what’s called a unifying diagnosis. Instead, they tell the patient, ‘Oh, you have irritable bowel. Oh, you have interstitial cystitis. Oh, you have fibro. Oh, you have chronic fatigue.’ They don’t say, ‘Wait a minute, how likely is it that one person would have six different problems that are not related in some way? Because these [small-fiber] nerves go everywhere in the body, one disease can cause many, many different symptoms. [Medical providers] have been looking at this from their own perspective of their medical specialty and not seeing the big picture. Small-fiber polyneuropathy brings the big picture in that it can explain a lot of different symptoms.”
Oaklander’s research found SFPN in fibromyalgia patients is most often caused by an autoimmune response.
“We think we have discovered a new disease where there is what’s called nerve-specific autoimmunity that’s targeting the small fibers,” she said. “It makes sense logically. There are autoimmune diseases that target every single cell in the body. Why wouldn’t there be some patients who have [an] autoimmune [response] directed at the small fibers?
“But it’s a new discovery, and when you make a new discovery, it really takes a long time and a lot of work to get it established. We have a bunch of papers that have evidence for it, but it’s far from proven at this point.”
Oaklander has been using intravenous immunoglobulin (IVIG) to treat patients with SFPN caused by immune dysfunction.
“We have patients who have done much, much better once they’ve started on immunotherapy to where they’ve been able to get out of bed and go back to work,” she said.
And some patients have been cured.
The problem is IVIG is extremely expensive; treatment can run around $100,000 per year. It’s hard to get insurance coverage for it, so Oaklander and her team are trying to identify a more affordable treatment.
“IVIG is the best we can do right now, and it’s been a breakthrough, but we’d like to find something that’s cheaper, much more available and easier to take,” Oaklander said. “To do that, we’ve actually got to go to the molecular level and the genetic level and understand what’s happening. We have a large National Institutes of Health grant application to prepare for randomized clinical trials of immunotherapy for these patients.”
For now, Oaklander believes patients can benefit from the existing research linking fibromyalgia and SFPN.
“Given that a dozen different [research] authors have published papers that say small-fiber polyneuropathy underlies or contributes to fibromyalgia, it’s fair to say that every single person diagnosed with fibromyalgia should be asking their doctor if they could have small-fiber polyneuropathy as an underlying cause,” she said.
Physicians of patients who live near Massachusetts General Hospital in Boston can request a skin biopsy test by filling out this requisition form. For those living in other areas, visit Neuropathy Commons’ Find Care portal to locate a specialist near you to be evaluated for SFPN.
Donna Gregory Burch was diagnosed with fibromyalgia in 2014 after several years of unexplained pain, fatigue and other symptoms. She was later diagnosed with chronic Lyme disease. Donna covers news, treatments, research and practical tips for living better with fibromyalgia and Lyme on her blog, FedUpwithFatigue.com. You can also find her on Facebook and Twitter. Donna is an award-winning journalist whose work has appeared online and in newspapers and magazines throughout Virginia, Delaware and Pennsylvania. She lives in Delaware with her husband and their many fur babies.