NEW YORK (Reuters Health) - The risk of rheumatoid factor (RF) -seropositive rheumatoid arthritis (RA) is significantly increased among current smokers with a classic genetic risk factor, according to a study published in the October issue of Arthritis and Rheumatism.
The main genetic risk factor for RA is the shared epitope (SE) of HLA-DR and smoking is an important environmental risk factor, Dr. Leonid Padyukov, of Karolinska Hospital, Stockholm, Sweden, and colleagues observe. They examined whether a gene-environment interaction exists between SE genes and smoking in the etiology of RF-seropositive RA.
A total of 858 subjects with RF-seropositive or RF-seronegative RA and 1048 controls took part in the population-based, case-control study. The researchers classified the cases and controls according to their smoking status and HLA-DRB1 genotypes.
Never smokers with SE genes had a relative risk of RF-seropositive RA of 2.8. Current smokers without SE genes and those with SE genes had relative risks of 2.4 and 7.5. The relative risk of RF-seropositive RA for current smokers with double SE genes was 15.7.
The risk of developing RF-seronegative RA was not increased by smoking, SE genes, or the combination of these factors.
These findings, the investigators conclude, further emphasize the necessity of subphenotyping of RA “in all pathogenetic and genetic studies of this disease.”
Source: Arthritis Rheum 2004;50:3085-3092. [ Google search on this article ]
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