Chronic fatigue syndrome has no cure and reliable treatments remain elusive, but new research links it to changes in 17 immune-system signaling proteins called cytokines.
That suggests inflammation plays a part in the disease, which can persist for years, according to researchers at Stanford University Medical Center. They said their findings could help doctors diagnose chronic fatigue and gauge its severity.
It is also known as myalgic encephomyelitis, or ME/CFS.
"There's been a great deal of controversy and confusion surrounding ME/CFS -- even whether it is an actual disease," study senior author Dr. Mark Davis, said in a hospital news release. "Our findings show clearly that it's an inflammatory disease and provide a solid basis for a diagnostic blood test."
Davis is the director of Stanford's Institute for Immunity, Transplantation and Infection.
Chronic fatigue syndrome affects more than 1 million people in the United States. Women are more often affected than men, and the condition often flares up first during the teen years, then again in a person's 30s, the authors said.
"Chronic fatigue syndrome can turn a life of productive activity into one of dependency and desolation," lead author Dr. Jose Montoya said in the news release. Montoya is a professor of infectious diseases at the medical center.
Some people recover within a year without treatment. But it persists for decades in most.
Besides debilitating fatigue not relieved by rest, chronic fatigue syndrome may cause flu-like symptoms, as well as mental fuzziness or "brain fog." Some people also develop heart problems, diarrhea, constipation or muscle pain. The wide-ranging symptoms have made it tricky for doctors to diagnose.
"I have seen the horrors of this disease, multiplied by hundreds of patients," Montoya said. "It's been observed and talked about for 35 years now, sometimes with the onus of being described as a psychological condition. But chronic fatigue syndrome is by no means a figment of the imagination. This is real."
Antiviral and anti-inflammatory drugs have helped ease symptoms, and medications that target the immune system have also had some success.
Hoping to pinpoint a possible trigger for the condition, the Stanford researchers analyzed blood samples from 192 people with chronic fatigue and 392 healthy people. The chronic fatigue patients had been battling symptoms more than a decade, on average.
Researchers took into account how long patients had been ill and the severity of their symptoms. Then, they analyzed levels of 51 cytokines.
Of these proteins, 17 are linked with disease severity and 13 are pro-inflammatory, according to the study. Pro-inflammatory means they act to make the disease worse.
Researchers noted that one of the proteins is more common in women's blood than in men's, which could shed light on why chronic fatigue is more common among women. The authors said their findings could be used to improve diagnosis and treatment of the disease.
"For decades, the 'case vs. healthy controls' study design has served well to advance our understanding of many diseases," Montoya said. "However, it's possible that for certain pathologies in humans, analysis by disease severity or duration would be likely to provide further insights."
The study was published online July 31 in the Proceedings of the National Academy of Sciences.
The U.S. National Library of Medicine provides more information on chronic fatigue syndrome.
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