TUESDAY, Aug. 6 (HealthDay News) -- About half of fibromyalgia patients have damage to nerve fibers in their skin and other evidence of a disease called small-fiber polyneuropathy (SFPN), a small new study finds.

Fibromyalgia is characterized by symptoms such as pain and tenderness, fatigue, and sleep and memory problems. The disorder has no known causes and few effective treatments.

The study of 27 fibromyalgia patients found that 13 had evidence of small-fiber polyneuropathy. Unlike fibromyalgia, small-fiber polyneuropathy is known to be caused by specific medical conditions, some of which can be treated and sometimes cured, according to the Massachusetts General Hospital researchers.

The findings were published online in the journal Pain.

"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," study corresponding author Dr. Anne Louise Oaklander, director of the hospital's nerve injury unit and an associate professor of neurology at Harvard Medical School, said in a hospital news release.

"Until now, there has been no good idea about what causes fibromyalgia, but now we have evidence for some but not all patients. Fibromyalgia is too complex for a 'one size fits all' explanation," Oaklander said.

"The next step of independent confirmation of our findings from other laboratories is already happening, and we also need to follow those patients who didn't meet SFPN criteria to see if we can find other causes," she said. "Helping any of these people receive definitive diagnoses and better treatment would be a great accomplishment."

Fibromyalgia affects 1 percent to 5 percent of people in Western nations, and many more women than men.

More information

The American Academy of Family Physicians has more about fibromyalgia.