Smoking Further Implicated in RA rheumatoid arthritis

Smoking is a major preventable factor contributing to the development of antibody-positive rheumatoid arthritis in genetically susceptible individuals, a large Swedish case-control study found. 

The study, encompassing more than 2,000 cases and controls, found that in RA patients testing positive for anticitrullinated protein/peptide antibody (ACPA), 35% of the risk for the disease was attributable to smoking, according to Henrik Kдllberg, MD, of the Karolinska Institute in Stockholm, and colleagues. 

And in RA patients carrying two copies of the HLA-DRB1 shared epitope -- known to increase risk for the disease -- 55% of RA risk was attributable to smoking, Kдllberg and co-authors reported online in the Annals of the Rheumatic Diseases. 

Cigarette smoking has long been linked with RA, with a current hypothesis suggesting that citrullination -- a process by which the amino acid arginine is replaced by citrulline -- helps trigger an immune response in those who carry the susceptibility genes.