But her success came at a price. “The day after I turned in my manuscript, my health collapsed,” says Hillenbrand. “You want so much to defy this illness and live on your own terms. I hoped I could get away with it, but I couldn’t.” Debilitating symptoms of chronic fatigue, and the devastating vertigo that accompanied them, had returned with a vengeance.
Medical researchers have long sought a reliable diagnostic test for chronic fatigue syndrome, which a physician can identify only after ruling out the many other possible causes of severe fatigue. Now CDC researchers may be on the verge of developing such a test, based on analyzing patients’ genetic material.
Essentially, the researchers have found that chronic fatigue syndrome prompts a complex physiological response that leads to a telltale pattern in gene output. They extracted from the patients’ blood cells the intermediate genetic material known as messenger RNA, which is produced when genes are instructing cells to grow, divide, fend off an invader or otherwise be active. Using a recently developed technology called gene expression microarrays, the researchers tested the patients’ RNA, inferring from it which genes had been active—that is, “expressing” their genetic code, as scientists say. The technique enables scientists to probe for tens of thousands of genes simultaneously and determine which ones are active, or “on,” and which are inactive, or “off.” Chronic fatigue syndrome, the CDC researchers speculate, might yield a sort of genetic signature, a pattern of the genes’ expression.
Analyzing blood samples from chronic fatigue syndrome patients and healthy people in the Atlanta area, the researchers posed a simple question: Could the genetic tool tell the difference between the samples? “The answer is: yes, it can,” says Suzanne Vernon, a molecular epidemiologist and the study’s lead researcher. She cautions that more work is needed to confirm the findings in other populations, for example. But she says the results are “very exciting,” and she predicts that microarrays will someday routinely diagnose chronic fatigue syndrome, whatever the underlying cause.
“Most CFS experts would agree that there may be several subcategories of [the disorder]—due to an infectious agent or to stress and so forth,” says Vernon. “I anticipate seeing an underlying gene-expression pattern common to all CFS patients but, in addition, some unique genes expressed that correspond to each subgroup.”