PTPN22 and rheumatoid arthritis: Previous linkage and candidate gene studies have identified several regions that predispose to RA, including the HLA-DRB1 and PTPN22. We conducted genome-wide linkage analysis with 128 affected individuals from 60 families in a Canadian cohort that were genotyped using the Illumina linkage panel and genome-wide association analysis with 158 affected individuals from the same cohort that were genotyped using the Affymetrix 100 K platform.