Juvenile idiopathic arthritis (JIA) is an autoimmune disease characterized by persistent chronic arthritis. Disease risk is believed to be influenced by both genetic and environmental factors. It is well established that the PTPN22 single nucleotide polymorphism (SNP) rs2476601 is associated with JIA susceptibility. It was recently reported in an Australian study that this association is restricted to females and is not observed in males. A significant source of inconsistency amongst the literature on autoimmune disease susceptibility genes stems from an inability to replicate genetic findings across different racial or ethnic groups. We therefore attempted to generate further evidence of the female-specific association of rs2476601 in a homogeneous Greek population.
We genotyped rs2476601 in 128 Caucasian JIA patients (70.3 % female) and 221 healthy controls (28.1 % female) from Northern Greece. Overall, PTPN22 was associated with increased risk of JIA in this Greek sample (OR = 2.3, 95 % CI 1.1 - 5.1, p = 0.038). Sex-stratified analyses showed that, once again, the risk association was restricted to females (Female: OR = 19.9, 95 % CI 1.2 - 342, p = 0.0016; Male: OR = 1.1, 95 % CI 0.3 - 3.1, p = 0.94) supporting the prior findings.
Our data demonstrates that this sex-specific pattern of association is broadly applicable to different populations, and provides further impetus to undertake mechanistic studies to understand the impact of sex on PTPN22 in JIA.