Association between the PTPN22+1858 C/T polymorphism and psoriatic arthritis

Introduction: The purpose of the present study was to investigate the frequency of the PTPN22 +1858 C/T single nucleotide polymorphism (SNP) (rs 2476601), previously shown to be associated with several autoimmune diseases, in patients with psoriatic arthritis (PsA) in comparison with population based controls. Methods: A total of 291 patients (145 male/146 female, mean age (+/- S.D.) 52.2 (+/- 13.1) years) with PsA were examined clinically, by standard laboratory tests and their DNA was genotyped for the SNP rs2476601 (PTPN22 +1858 C/T). Allelic frequencies were determined and compared with 725 controls. Results: Carriage of the risk allele, PTPN22+1858T, showed a significant association with patients with PsA compared with controls (chi(2) = 6.56, P = 0.010, odds ratio (OR) 1.49; 95% confidence interval (CI) 1.10 to 2.02). A significantly higher proportion of carriers of the risk allele (T) had significantly more deformed joints (n +/- SEM) (5.9 +/- 1.2 vs 2.8 +/- 0.5; P = 0.005). Conclusions: In this study the +1858T allele of the PTPN22 gene, known to be associated with several autoimmune diseases, was associated with PsA. The finding of significantly more joints with deformities among carriers of the T variant could indicate a more aggressive phenotype of disease.