Summary: About half of a small group of patients with fibromyalgia – a common syndrome causing chronic pain and other symptoms – has been found to damage nerve fibers in the skin and show other signs of an illness called Small Fiber Polyneuropathy (SFPN). Unlike fibromyalgia, the SFPN has an obvious pathology and is known to be caused by specific medical conditions, some of which can be treated and sometimes cured.
About half of a small group of patients with fibromyalgia – a common syndrome causing chronic pain and other symptoms – has been found to damage nerve fibers in the skin and to show other signs of a disease called polyneuropathy with small fibers (SFPN). Unlike fibromyalgia, which has no known cause and few effective treatments, SFPN has an obvious pathology and is known to be caused by specific medical conditions, some of which can be treated and sometimes cured. The study of Massachusetts General Hospital (MGH) researchers will appear in the PAIN journal and has been published online.
“This provides one of the first objective evidence of a mechanism behind some cases of fibromyalgia, and identifying an underlying cause is the first step toward finding better treatments,” said Anne Louise Oaklander, MD , PhD, Director of the Nerve Unit in the Department of Neurology at the MGH and corresponding author of the pain paper.
The term fibromyalgia describes a set of symptoms – including generalized chronic pain, increased pressure sensitivity and fatigue – that would affect 1 to 5% of people in western countries, more commonly women. A diagnosis of fibromyalgia has been recognized by the National Institutes of Health and the American College of Rheumatology, but its biological basis has remained unknown. Fibromyalgia shares many symptoms with the SFPN, a recognized cause of chronic generalized pain for which there are accepted objective tests.
Designed to investigate possible links between the two conditions, this study included 27 adult patients diagnosed with fibromyalgia and 30 healthy volunteers. Participants were provided with a battery of tests to diagnose FNS, including physical examination-based neuropathy assessments and questionnaire responses, skin biopsies to assess the number of nerve fibers in the lower legs, and tests. autonomous functions such as heart rate, blood pressure and sweating.
Questionnaires, evaluations, and skin biopsies all revealed significant levels of neuropathy in patients with fibromyalgia, but not in the control group. Of the 27 patients with fibromyalgia, 13 had a marked reduction in nerve fiber density, abnormal autonomic function tests, or both, indicating the presence of FNCS. Participants who met the FNFP criteria were also screened for known causes of the disorder and none of them gave results suggestive of diabetes, a common cause of PNDS, but two had the hepatitis C virus, which can be successfully treated, and more than half had signs of immune system dysfunction.
“Until now, the causes of fibromyalgia were not well known, but we now have evidence for some patients, but not all. Fibromyalgia is too complex for a “one size fits all” explanation, says Oaklander, an associate professor of neurology at Harvard Medical School. “The next step of independent confirmation of our results by other labs is already underway and we also need to follow patients who do not meet the FNFP criteria to see if we can find other causes. Helping one of these people to receive a definitive diagnosis and a better treatment would be a great achievement. “