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Fibromyalgia patients’ pain might stem from small-fiber polyneuropathy
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Almost half of patients diagnosed with fibromyalgia tested positive for small-fiber polyneuropathy, a peripheral nerve disease that might cause their chronic widespread pain, according to recent study results.
“Until now, there has been no good idea about what causes fibromyalgia, but now we have evidence for some but not all patients,” researcher Anne Louise Oaklander, MD, PhD, director of the Nerve Injury Unit at Massachusetts General Hospital’s neurology department, said in a press release. “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 toward finding better treatments.”
Anne Louise Oaklander
Oaklander and colleagues studied 27 patients with fibromyalgia (mean age, 46.5 years; 74.1% women; mean illness duration, 19.1 years) and 30 matched controls (mean age, 44.8 years; 80% women) without fibromyalgia to analyze small-fiber polyneuropathy (SFPN)-associated symptoms. The fibromyalgia cohort met ACR 2010 diagnostic criteria and had physician-diagnosed evidence of fibromyalgia. Michigan Neuropathy Screening Instrument (MNSI), the Utah Early Neuropathy Scale (UENS), distal-leg neurodiagnostic skin biopsies and autonomic-function testing (AFT) were used for testing.
SFPN was diagnosed in 41% of biopsies among fibromyalgia patients compared with 3% of controls. Fibromyalgia patients had greater MNSI (5.8 ± 0.6 vs. 1.3 ± 0.3; P<.001) and UENS scores (3.1 ± 0.7 vs. 0.5 ± 0.2; P<.001) compared with controls.
“Abnormal AFTs were equally prevalent, suggesting that fibromyalgia-associated SFPN is primarily somatic,” the researchers reported.
Blood tests were conducted on the 13 fibromyalgia patients diagnosed with SFPN. Eight patients had normal glucose-tolerance test results, according to ADA criteria; two patients tested positive for hepatitis C.
“This study provides objective evidence that almost half of a small sample of patients labeled with [fibromyalgia] have objective evidence of a neurological cause of their [chronic widespread pain] and other symptoms of fibromyalgia, namely SFPN, a distinct peripheral nerve disease,” the researchers concluded.
Disclosure: The researchers report no relevant financial disclosures.
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