Objectives: To compare the magnetic resonance imaging (MRI) morphology of inflammatory and chronic lesions in the sacroiliac joints (SIJs) and spine between patients with non-psoriatic and psoriatic non-radiographic axial spondyloarthritis (axSpA and p-axSpA, respectively).
Methods: Patients from the EMBARK trial (NCT01258738) with axSpA (n=179) and p-axSpA (n=24) who had MRI data available were compared in terms of baseline demographics, clinical characteristics, and the frequency (n/N [%]) and distribution of inflammatory and structural SIJ and spinal lesions.
Results: Patients with p-axSpA were on average older (35.1 years vs. 31.7 years, p=0.047), had a higher occurrence of asymmetric sacroiliitis (54.2% vs. 29.6%, p=0.042), and a lower occurrence of human leukocyte antigen (HLA)-B27 positivity (41.7% vs. 73.7%, p=0.010) than patients with axSpA. There were no significant differences in the frequency of lesions in any of the SIJ or spinal quadrants between the two subgroups.
Conclusions: These data suggest that differences between axSpA and p-axSpA extend beyond presence of psoriasis, and include age, SI symmetry, and HLAB27 status. These findings may help explain the morphotype-phenotype relationship across axSpA, similar to those described in older radiographic studies.