Expression of Major Histocompatibility Complex (MHC) class II human leucocyte antigen-DRB1 (HLA-DRB1) allele has been found in RA patients and combination of HLA-DRB1 Shared Epitope (SE) alleles and smoking was known to be the risk factor for developing RA.5,6 Up to date, periodontitis has been found to be a risk factor for RA. The gene discussed is HLA-DRB1; the disease is periodontitis.