Background : To investigate the association between 12 single nucleotide polymorphisms (SNPs) located on ERAP1 and IL23R with the presence of inflammation on the sacroiliac joint (SIJ) or spinal magnetic resonance imagery (MRI) in an early onset spondyloarthritis (SpA) cohort. Methods : All the patients included in the DESIR cohort with an axial SpA and available DNA at baseline were enrolled in this study (n = 645 patients) and underwent a clinical examination, CRP assay, SIJ and spinal MRI scans. Six SNPs located on ERAP1 (rs30187, rs27044, rs27434, rs17482078, rs10050860, rs2287987) and six SNPs located on IL23R (rs1004819, rs10489629, rs1343151, rs2201841, rs10889677, rs11209032) were genotyped. Univariable analyses were performed to test the association between the genotypes and SIJ and spinal MRI inflammation, as well as disease activity based on Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing SpondylitisDisease Activity Score C-Reactive Protein (ASDAS-CRP) and CRP. Results : One SNP located on ERAP1 (rs27434) and haplotype CCT of ERAP1 were associated with SIJ inflammation detected by MRI, but these associations were below the Bonferroni corrected threshold of significance. However, one SNP (rs1004819) located on IL23R was associated with SIJ MRI inflammation (rs1004819: TT 42.3%, CT 40.5%, CC 26.5%, p = 0.0005). This locus was also significantly associated with Spondyloarthritis Research Consortium of Canada scores while no association with another inflammatory parameter such as BASDAI, ASDAS-CRP, CRP or Berlin MRI score was identified in this population. Conclusion : One locus of the IL23R gene was associated with SIJ MRI inflammation and might be a marker of more active disease in recent onset SpA.