Thus, we have investigated the impact of genetic variants of MBL on RA risk by using information from a large population-based case-control study of incident RA (Epidemiological Investigation of Rheumatoid Arthritis, or EIRA), and this enabled us to dissect this criteria-based syndrome into subgroups on the basis of autoantibody status and environmental (smoking) and genetic (SE and PTPN22) risk factors that are known to be associated mainly with the autoantibody-positive form. Here, PTPN22 is linked to rheumatoid arthritis.