Fibromyalgia is a disorder affecting about two percent of people with symptoms such as widespread pain, fatigue and sensitivity to pressure. The cause and cure for fibromyalgia is unknown.
Small-fiber polyneuropathy (SFPN) is a disease with similar symptoms to fibromyalgia. SFPN, however, has known causes such as diabetes and hepatitis. SFPN can be treated.
In a recent study, half of the fibromyalgia patients tested had damaged nerve fibers. They also showed signs of having unrecognized SFPN, which might have caused their symptoms. This could mean that some people with fibromyalgia might have SFPN, which could be treated.
Anne Louise Oaklander, MD, PhD, director of the Nerve Injury Unit at Massachusetts General Hospital, and colleagues conducted this study to explore the relationship between fibromyalgia and small-fiber polyneuropathy (SFPN).
The researchers studied 27 patients diagnosed with fibromyalgia and 30 patients without fibromyalgia.
The researchers used several tests, including skin biopsies (removal of a small sample of skin) to evaluate the number of nerve fibers in the lower leg and autonomic function testing, which is a non-invasive test of the autonomic nervous system which controls involuntary bodily functions like breathing, heart rate and digestion.
They also used the Michigan Neuropathy Screening Instrument, which involves two parts: a written survey answered by the patients and a physical exam.
The researchers also used the Utah Early Neuropathy Scale to conduct a physical examination of each participant.
This study found that 41 percent (13) of skin biopsies from fibromyalgia participants were positive for SFPN. Of the non-fibromyalgia group, only three percent were positive for SFPN.
Autonomic function testing was similar for both the fibromyalgia and the non-fibromyalgia group.
The participants whose skin biopsies suggested SFPN also had blood tests to identify the cause of the condition. The blood tests revealed that none of the participants had diabetes. Two of the participants were infected with the hepatitis C virus, which is treatable. Over half (8) of the participants who tested positive for SFPN appeared to have a problem with their immune system.
"This provides some of the first objective evidence of a mechanism behind some cases of fibromyalgia, and identifying an underlying cause is the first step towards finding better treatments," said Dr. Oaklander.
She said these findings will need to be confirmed through additional studies, which have already begun.
The researchers also hope to follow up on the patients who did not appear to have SFPN.
This study was published online June 5 in the journal Pain.
The study was funded by grants from Public Health Service, the Department of Defense and a donation from Jane Cheever Powell. The authors reported no conflicts of interest.