Functional variants of ERAP1 gene are associated with HLA-B27 positive spondyloarthritis.

We investigated two nonsynonymous variants (rs30187 and rs27044) of ERAP1 gene in HLA-B27 positive individuals (150 spondyloarthritis and 108 controls) and in general ankylosing spondylitis (AS) patients (n = 137) vs random controls (n = 139). Both single nucleotide polymorphisms (SNPs) were associated with the risk of spondyloarthritis [odds ratio (OR) 1.80, 95% confidence interval (CI) 1.24-2.62, P = 0.001 for rs30187, OR 1.58, 95% CI 1.07-2.34, P = 0.02 for rs27044]. The CC haplotype was a protective factor (P = 0.002), while the TG haplotype was a risk factor (P = 0.01) for spondyloarthritis. The SNP rs30187 was also associated with the risk of HLA-B27+ AS. For the general group of AS, the carriers of minor alleles showed an increased risk for the disease (OR 1.92, 95% CI 1.17-3.13 for rs30187, OR 1.74, 95% CI 1.08-2.80 for rs27044). This is the first study that shows the association of ERAP1 gene variants and haplotypes with HLA-B27 positive spondyloarthritis.