Does psoriatic axial spondyloarthritis phenotype correlate with imaging morphotype?

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).

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.

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.

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.