This study aimed at examining the association of the single nucleotide 
polymorphism (SNP) in the protein tyrosine phosphatase gene (PTPN22) with the 
risk of rheumatoid arthritis (RA) in a Chinese population. A total of 200 RA 
patients and age and gender-matched healthy controls were recruited. Their 
genotypes and allelic frequency were determined by the TaqMan-MGB probe-based 
polymerase chain reaction (PCR). The frequencies of the CC genotype and C allele 
in RA patient group were significantly higher than that of controls (P < 0.01 or 
P < 0.05) with an odds ratio of 1.67, respectively. These data suggest, the CC 
genotype and C allele of the -1123G > C in the PTPN22 gene are associated with 
an increased risk for RA in Chinese population. Therefore, the CC genotype and C 
allele of the -1123G > C in the PTPN22 gene may be used as a genetic marker for 
the predisposition of RA in Chinese.