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__Background__ Large-scale genetic studies have reported several loci associated with specific disorders involving uveitis. Our aim was to identify genetic risk factors that might predispose to uveitis per se, independent of the clinical diagnosis, by performing a dense genotyping of immune-related loci. __Methods__ 613 cases and 3693 unaffected controls from three European case/control sets were genotyped using the Immunochip array. Only patients with noninfectious non-anterior uveitis and without systemic features were selected. To perform a more comprehensive analysis of the human leucocyte antigen (HLA) region, SNPs, classical alleles and polymorphic amino acid variants were obtained via imputation. A meta-analysis combining the three case/control sets was conducted by the inverse variance method. __Results__ The highest peak belonged to the HLA region. A more detailed analysis of this signal evidenced a strong association between the classical allele HLAA* 2902 and birdshot chorioretinopathy (p=3.21E-35, OR=50.95). An omnibus test yielded HLA-A 62 and 63 as relevant amino acid positions for this disease. In patients with intermediate and posterior uveitis, the strongest associations belonged to the rs7197 polymorphism, within HLA-DRA ( p=2.07E-11, OR=1.99), and the HLA-DR15 haplotype (DRB1*1501: p=1.16E-10, OR=2.08; DQA1*0102: p=4.37E-09, OR=1.77; DQB1*0602: p=7.26E-10, OR=2.02). Outside the HLA region, the MAP4K4/IL1R2 locus reached statistical significance (rs7608679: p=8.38E-07, OR=1.42). Suggestive associations were found at five other loci. __Conclusions__ We have further interrogated the association between the HLA region and non-infectious non-anterior uveitis. In addition, we have identified a new non-HLA susceptibility factor and proposed additional risk loci with putative roles in this complex condition.

Birdshot chorioretinopathy (BSCR) is a rare form of autoimmune uveitis that can lead to severe visual impairment. Intriguingly, >95% of cases carry the HLA-A29 allele, which defines the strongest documented HLA association for a human disease. We have conducted a genome-wide association study in 96 Dutch and 27 Spanish cases, and 398 unrelated Dutch and 380 Spanish controls. Fine-mapping the primary MHC association through high-resolution imputation at classicalHLA loci, identified HLA-A*29:02 as the principalMHCassociation (odds ratio (OR) 5 157.5, 95% CI 91.6-272.6, P = 6.6 × 10-74). We also identified two novel susceptibility loci at 5q15 nearERAP2 (rs7705093;OR 5 2.3,95%CI 1.7-3.1, for the T allele,P = 8.6 × 10-8) and at 14q32.31 in theTECPR2 gene (rs150571175;OR 5 6.1,95%CI 3.2-11.7, for theAallele,P = 3.2 × 10-8). The association nearERAP2was confirmed in an independent British case-control samples (combined meta-analysis P = 1.7 × 10-9). Functional analyses revealed that the risk allele of the polymorphism near ERAP2 is strongly associated with high mRNA and protein expression of ERAP2 in B cells. This study further defined an extremely strong MHC risk component in BSCR, and detected evidence for a novel disease mechanism that affects peptide processing in the endoplasmic re