Persisting high disease activity according to the ASDAS is associated with accelerated radiographic spinal progression in early axSpA.

Non-radiographic axial spondyloarthritis (nr-axSpA) represents a subtype of axial spondyloarthritis (axSpA) with no significant structural damage in sacroiliac joints and spine. In addition, patients with nr-axSpA demonstrate a substantial burden of illness, and a considerable share of them might progress to radiographic axSpA (r-axSpA) over time. The amount and quality of published data allows crude estimation of progression rate and factors related to a higher risk of progression. Areas covered: This review discusses the available data reporting the rates and predictors of radiographic progression in the sacroiliac joints and in the spine in patients with nr-axSpA as well as predisposing factors for such a progression. Expert commentary: Most of the studies report about 10-40% of patients with nr-axSpA to progress to r-axSpA over a period of 2-10 years. Multiple risk factors for the radiographic sacroiliitis progression are outlined and explored. There are not enough data to presume that any treatment modality may influence progression from nr-axSpA to r-axSpA, with TNFi showing some promising results. Radiographic progression in the spine is in general low in nr-axSpA; thus, long-term studies are required to investigate the natural course of the progression and possible treatment effects.

Objectives Osteitis condensans ilii (OCI) has become an important differential diagnosis for axial spondyloarthritis (axSpA). The objective of this matched case–control study was to investigate demographic, clinical, laboratory and MRI characteristics of OCI as compared with axial spondyloarthritis (axSpA). Methods A total of 60 patients diagnosed with OCI were included in the final analysis. From 27 of these patients, MRIs of the sacroiliac joints were available. OCI patients were matched with a 1:1 ratio by back pain duration to patients with definite axSpA in order to compare clinical, laboratory and MRI characteristics. Results The OCI patients were nearly all females (96.7 vs 46.7%), had a significantly lower prevalence of inflammatory back pain (39.5 vs 88.9%), a significantly lower percentage of HLA-B27 positives (35.2 vs 80.0%) and a lower prevalence of the majority of other SpA features as compared with axSpA patients. Interestingly, there was no difference in the prevalence of osteitis in the sacroiliac joints (92.6 vs 85.2% in OCI and axSpA, respectively, P = 0.44), but there was a difference in the prevalence of erosions (7.4 vs 66.7%, respectively, P = 0.0001). In addition, in OCI nearly all lesions were localized in the anterior part of the sacroiliac joints while in axSpA lesions were localized predominantly in the middle part of the joint (for osteitis: 96 vs 4% in OCI and 28.6 vs 71.4% in axSpA; P = 0.0002 for the inter-group difference). Conclusion Clinical and imaging features of OCI compared with axSpA are described that should help in differential diagnosis.