Association of a functional single‐nucleotide polymorphism of PTPN22, encoding lymphoid protein phosphatase, with rheumatoid arthritis and systemic lupus erythematosus

Abstract

Objective: To assess the possible association between the PTPN22 gene 1858C→T polymorphism and the predisposition and clinical expression of 2 systemic autoimmune diseases, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Methods: Our study population consisted of 826 RA patients, 338 SLE patients, and 1,036 healthy subjects. All subjects were of Spanish Caucasian origin. Genotyping of the PTPN22 gene 1858C→T polymorphism was performed by real‐time polymerase chain reaction technology, using the TaqMan 5′‐allele discrimination assay. Results: The overall distribution of genotypes in the RA patients was significantly different from that in the controls (P = 0.005, by chi‐square test with 2 × 3 contingency tables). We observed a statistically significant difference in the distribution of the PTPN22 1858T allele between healthy subjects (7.4%), and RA patients (10.4%) (P = 0.001, odds ratio [OR] 1.45 [95% confidence interval (95% CI) 1.15–1.83]). In addition, PTPN22 1858 C/T and T/T genotypes were present at a significantly higher frequency in SLE patients than in controls (P = 0.02, OR 1.55 [95% CI 1.05–2.29]). Differences were also observed when allele frequencies were compared, with the PTPN22 1858T allele being present at a higher frequency among SLE patients (P = 0.03, OR 1.45 [95% CI 1.01–2.09]). Conclusion: These results suggest that the PTPN22 1858T allele may confer differential susceptibility to RA and SLE in the Spanish population.