Objective Ankylosing spondylitis (AS) is an autoimmune disease that mainly affects the sacroiliac joints and the spine of the lower back. The disease is strongly associated with HLA–B27. Additional genes, single‐nucleotide polymorphisms, and molecular components have been identified to be associated with AS, but the exact mechanism that drives disease development remains poorly understood. The killer cell immunoglobulin‐like receptors (KIRs) are regulators of cytotoxicity of natural killer cells and T cell subsets and may be relevant in binding to HLA–B27 and the development of AS. We undertook this study to identify possible associations of KIR genotype with susceptibility to AS and disease characteristics including the presence of the HLA–B27 allele, disease severity, and uveitis. Methods We performed complete genotyping of the KIR locus in 303 Caucasian AS patients, 119 randomly selected healthy Caucasian controls, and 50 HLA–B27–positive healthy Caucasian controls by multiplex ligation‐dependent probe amplification assay for detection of gene presence and copy number. Results We did not observe a significant association of any specific KIR gene or haplotype with susceptibility to AS or any other clinical manifestation. Disease severity, as measured by fulfilling the criteria for treatment with tumor necrosis factor blocking therapy, was linked to a lower number of genes for the functional variant of KIR3DL1 (P = 0.007). Conclusion Our exploratory study indicates that KIR genes are not a major risk factor for susceptibility to AS. However, the data do suggest a role for KIRs in progression of the disease, whereby KIR3DL1 has a protective effect against the more severe manifestations of AS.

Objectives The primary aim is to evaluate signs of inflammation on MRI of sacroiliac joints (SIJ)/spine in inflammatory back pain (IBP) patients suspected of nr-axSpA with high disease activity. Secondary aims are to describe the onset of new inflammatory lesions at MRI after 6 months and to evaluate gender differences in the presence of inflammation. Method Consecutively, patients with IBP with at least two spondyloarthritis features, high disease activity (BASDAI ≥ 4), and who were TNFi naïve, had a MRI of SIJ and spine. In the absence of active lesions, MRI was repeated after 6 months. MRI images were scored according to the Spondyloarthritis Research Consortium of Canada method. Results Sixty-nine patients were included (53% female), of whom 39% showed signs of inflammation at the first MRI: 30.9% of the SIJ, 19.1% of the spine and 2.4% at both sites, irrespective of the CRP levels. Males more often showed inflammatory signs at the MRI of the SIJ and spine compared with females (45.5% vs. 33.3%). Consistently, the median SPARCC score was higher in males: for SIJ 14.0 (IQR 2.3-25.0) and for spine 11.5 (IQR 8.5-25.6). Only one patient (4.7%) without baseline inflammatory signs showed active lesions of SIJ after 6 months. Conclusions Almost 40% of the IBP patients suspected of nr-axSpA, with high disease activity, showed inflammatory lesions on MRI of SIJ and/or spine, which occurred more often in males compared with females. In the majority (95.3%), an MRI without inflammatory lesions remained negative after 6 months despite high disease activity. Key Points • Forty percent of inflammatory back pain patients with high disease activity showed inflammatory signs on MRI of the SIJ and/or spine. • Only 4% of baseline MRIs without inflammatory signs at baseline conversed to an MRI with inflammatory signs after 6 months. • Male inflammatory back pain patients with high disease activity showed more often inflammatory signs on MRI compared with females.