The PTPN22 gene maps to chromosome 1p13.2 within a haplotype block of conserved linkage disequilibrium (LD) spanning over 300 kb.[1] To investigate the possibility that further genetic variants within PTPN22 have a role in RA, coding regions within the gene were resequenced in USA people of white ethnic group-European ancestry and ten common haplotypes were tested for association with RA.[9] This analysis confirmed the predominant role in disease susceptibility conferred by the haplotype tagged by the Trp620 allele (minor allele of rs2476601: C>T) (haplotype ‘2’). The gene discussed is PTPN22; the disease is rheumatoid arthritis.