Testing for linkage and association with rheumatoid arthritis a ptpn22 promoter polymorphism reported to be associated and linked with type 1 diabetes in the Caucasian population

The PTPN22 single nucleotide polymorphism (SNP) +1858 C/T (rs2476601) was found to be linked and associated with rheumatoid arthritis (RA).1 However, the frequency of the susceptibility +1858T allele range from 2% to 15% of south to north Europeans, and is not observed in an Asian population, suggesting the involvement of other disease-associated PTPN22 polymorphisms.2–4 A study performed in the type 1 diabetes (T1D) Japanese population led to the identification of the PTPN22 – 1123 G/C SNP (rs2488457), for which the –1123G allele was found to be associated with T1D.5 This allele in linkage disequilibrium with +1858T was also tested in a familial T1D UK Caucasian sample. The transmission disequilibrium test (TDT) showed a significant excess of transmission of the –1123G allele compared with that …