Genes and smoking play role in rheumatoid arthritis
Recent genetic studies have revealed several new sites of genes that are risk factors for developing rheumatoid arthritis (RA). The strongest association with anti-citrullinated protein antibody (ACPA)-positive RA (ACPAs are autoantibodies detected in RA that are used as a major diagnostic tool) has been found for the HLA-DRB1 gene, and this site seems to play a central role in susceptibility to the disease in Caucasian populations. Previous studies have shown a high increase in the risk of ACPA-positive RA associated with smoking in those who have certain variations of the HLA-DRB1 gene. There are several types of such alleles related to a particular amino acid sequence known as shared epitope (SE). ACPAs occur in about 60 percent of RA patients and are closely linked to the presence of SE alleles. In fact, SE alleles are the strongest genetic risk factor for ACPA-positive RA.