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Polymorphism in interleukin-4 gene linked to severity of joint damage in rheumatoid arthritis
By Charlie Schick

An international team of investigators reports that variation in the interleukin-4 (IL-4) gene may influence the severity of joint damage among individuals with rheumatoid arthritis. The IL-4 gene is involved in inflammation, and previous studies have linked the gene to diseases such as multiple sclerosis and rheumatoid arthritis. The current study found that rheumatoid arthritis patients with the IL-4(2) form of the gene tend to have less damage to their joints than do those with other forms of the gene.

The IL-4(2) variant is one of three known forms of the gene. The same 70-letter sequence of DNA is repeated in each variant but at different lengths. The most common variant, IL-4(1), has three repeats, while the IL-4(2) variant is less common and has two repeats. The rarest variant, IL-4(3), has four repeats. This type of polymorphism is called a VNTR (variable number of tandem repeats).

Pierre Miossec, of the H˘pital Edouard Herriot, Lyon, France, and colleagues identified the form of IL-4 in hundreds of rheumatoid arthritis patients who had been classified according to the severity of joint disease. An analysis of the data suggested that IL-4(2) offers some protection against severe damage to joints. The study, which appears in the current issue of Rheumatology, included 335 rheumatoid arthritis patients and a control group of 104 unaffected individuals.

"This IL-4 VNTR gene polymorphism may be a protective factor for severe joint destruction in rheumatoid arthritis that could be used as a prognostic marker early in the course of the disease," the researchers conclude in their paper.

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Buchs, N. et al. IL-4 VNTR gene polymorphism in chronic polyarthritis. The rare allele is associated with protection against destruction. Rheumatology 39, 1126-1131 (October 2000).

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