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Axial spondyloarthritis with psoriasis or psoriatic spondylitis

Psoriatic arthritis (PsA) commonly affects peripheral joints. In up to a quarter of PsA patients, the spine may be involved and this is known as psoriatic spondylitis (PsSpA). An important research question is whether PsSpA and Axial Spondyloarthritis (AxSpA) with psoriasis are separate conditions or not. 

Separate conditions (splitter) or same conditions within a spectrum (lumper)


Psoriatic arthritis with axial involvement (psoriatic spondylitis, PsSpA)

Axial Spondyloarthritis (AxSpA) with psoriasis

Figure 1. Are PsSpA and AxSpA with psoriasis two separate or similar conditions?

There is overlap between PsSpA and AxSpA with psoriasis. This includes the presence of HLA-B27 positivity in most patients with these presentations. Depending on whether one is a lumper or splitter, the perspective of these conditions will be seen through the lenses of being the former or the latter.

Is there any new information that may help us understand these conditions? The presence of pure axial disease is in 2 to 5% of all psoriatic arthritis (PsA) patients. Abstract 1775 (Kwok T et al) showed that in the PsA cohort, 2% patients had isolated axial disease. These patients had a higher chance of HLA-B*27 positivity and lower HAQ scores at presentation. There does not appear to be any predictors over time for the development of peripheral disease amongst patients who present with isolated axial disease.

The ASAS-PerSpA study, a cross-sectional database, aims to evaluate the clinical characteristics in the PsSpA group. Abstract 1790 (Sawada H et al) showed that there is variable level of axial involvement in PsA (32-43%) across different countries and regions. There were also differences in the disease activity and treatments in the different countries and regions. This shows that the assessment and comparison of PsSpA patients may be affected by the location of the region.

In general, axial symptoms occur later in the course of PsA. Often radiographic change in the spine is seen before the patient becomes symptomatic from joint pain or stiffness.  This observation is supported in abstract 1921 (Diaz P et al) where there is poor  correlation found between imaging and clinical findings. These abstracts at #ACR21 shows us that there are as many similarities as there are differences between PsSpA and AxSpA with psoriasis. These findings highlight the need for further research of the underlying mechanisms of axial involvement in PsA.



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