Gene Discovery May Help Guide Rheumatoid Arthritis Treatment
Aug. 31, 2000 -- Rheumatoid arthritis (RA) is a deforming, crippling disease that can lead to disability. But now, Canadian researchers have discovered a gene that can predict who will get the severe form of the disease and could help decide who needs aggressive treatment.
The Canadians, led by Abbas Khani-Hanjani, PhD, say that mutations on the interferon-gamma gene -- one of the major players in the body's immune system -- match up nicely with both severe rheumatoid arthritis and the mild form of the disease. The researchers report their findings in the Sept. 2 issue of The Lancet.
RA attacks the joints, most commonly the hands, wrists and knees. In its most severe forms it swells and distorts the joints, making movement painful and sometimes impossible. About 1-2% of the population has RA, but it is more likely to attack women than men.
Lead author Khani-Hanjani tells WebMD that the association reported by his team is the "strongest association ever reported." He says it is much stronger than previously reported genetic links.
Almost 75% of people with RA that had one type of the gene had severe RA, but few people with mild RA possessed this gene.
On the other hand, close to 65% of people with mild disease had another form of the same gene, while very few severe arthritis patients had this gene.
Co-author Andrew Chalmers, MD, associate professor of medicine at the University of Vancouver, tells WebMD that work is already underway to attempt to confirm the findings in a larger study, which will include several centers in the U.S. "We have enrolled about 400 patients thus far," he says. He says it "will be at least a year before we have results from this larger study."
In an editorial accompanying the study, W.E.R. Ollier of Manchester University Medical School in Manchester, England, writes that the results of the Canadian study are surprising because the association is so powerful. People with the "severe" form of the disease were 20 times more likely to develop severe rheumatoid arthritis. Previously discovered genes only increased the risk by 5-10 times.
Chalmers also cautions that it is too soon for this type of genetic testing to be used routinely. "First of all, it is very expensive," he says. The blood test using DNA technology, called PCR testing, costs about $100 to $200 (U.S.)."
But if the findings of this initial study can be reproduced, Chalmers says this type of testing may one day lead to treatments that will change the way RA develops in patients. For example, he says the tests could identify those patients who should receive more aggressive treatment, including expensive drugs such as Enbrel or Remicade, two strong therapies available in the U.S. but not in Canada.