Axial Disease and Psoriasis Increasingly Linked

Nearly one quarter of patients diagnosed with either psoriatic arthritis or ankylosing spondylitis, meet criteria for both conditions, a study shows. Furthermore, the pattern of axial disease seems to increasingly depend on the presence of skin psoriasis and HLA-B*27 alleles.

“Psoriatic spondyloarthritis (PsSpA) may represent a distinct endophenotype influenced by factors related to the presence of psoriasis, psoriatic nail disease and HLA-B*27 variants,” wrote Deepak R. Jadon of the Royal National Hospital for Rheumatic Diseases in the UK, and colleagues, in the Dec. 2 online issue of theAnnals of the Rheumatic Diseases. “This study indicates that PsSpA forms part of the spondyloarthritis (SpA) spectrum, flanked by psoriasis PsA and ankylosing spondylitis (AS). PsSpA has a similar disease burden as AS despite being less severe radiographically.

Researchers examined data from the Axial Disease in Psoriatic Arthritis study looking at patients with psoriatic arthritis and ankylosing spondylitis. The study was a prospective single-center cross-sectional observational study of 402 patients (201 with psoriatic arthritis and 201 with ankylosing spondylitis). Previously only a small number of studies compared the presence of spondyloarthritis (SpA) with psoriasis - otherwise referred to as psoriatic spondyloarthritis (PsSpA) - and ankylosing spondylitis (AS), but with inconsistent conclusions. 

A significant proportion of patients in the study with radiographic axial disease had PsSpA (118/275; 42.91%), and often had symptomatically silent axial disease (30/118; 25.42%). While 23.88% of PsA patients met the criteria for ankylosing spondylitis and 24.38% of ankylosing spondylitis cases met the criteria for psoriatic arthritis.

HLA-B*27 alleles were found in 7.09% of psoriatic arthritis patients (pPsA), 39.83% of psoriatic spondyloarthritis patients (PsSpA), and 89.17% or ankylosing spondylitis (AS) patients. HLA-B*27 antigen was found with significantly greater frequency in ankylosing spondylitis subjects than in psoriatic spondyloarthritis subjects (p<0.001), and in significantly fewer psoriatic arthritis subjects when compared to subjects with psoriatic spondyloarthritis (p<0.001). Patients with psoriatic spondyloarthritis experienced symptoms at a significantly younger age than those with psoriatic arthritis (P=0.01).

Inflammatory axial symptoms were found with greater frequency in those with ankylosing spondylitis (99.36%) than those with psoriatic arthritis (60.63%) and those with psoriatic spondyloarthritis (74.58%).  Furthermore, subjects with ankylosing spondylitis were significantly more likely to report axial symptoms than those with psoriatic spondyloarthritis (p<0.001). Psoriatic arthritis patients had significantly less current axial symptoms than those with psoriatic spondyloarthritis (p=0.03).

No statistically significant differences were found for disease activity scores or for axial metrology between groups however, function was found to be significantly worse in ankylosing spondylitis patients when compared with psoriatic spondyloarthritis patients (p=0.002). Nail disease was significantly worse in patients with psoriatic spondyloarthritis than those with psoriatic arthritis (p=0.01).

The authors found a significantly higher likelihood that patients with both sacroiliitis and spondylitis would test positive for the HLA-B*27 antigen (p<0.001).  Patients with ankylosing spondylitis were more likely than those with psoriatic spondyloarthritis to have complete sacroiliac joint ankylosis (p=0.004). Axial involvement severity based on radiographic findings was higher in men than women (p<0.001) and significantly higher in everyone with ankylosing spondylitis when compared to all patients with psoriatic spondyloarthritis (p<0.001).

Finally, while vertebral erosion severity was similar between those with ankylosing spondylitis and those with psoriatic spondyloarthritis, vertebral osteoproliferative severity was significantly worse in those with ankylosing spondylitis than in those with psoriatic spondyloarthritis.

Key points

• Psoriatic arthritis and ankylosing spondylitis have similar disease characteristics with overlapping diagnostic criteria.
• HLA-B*27 antigen positivity is strongly correlated with ankylosing spondylitis and the presence of axial inflammatory involvement.
• HLA-B*27 antigen was strongly associated with the presence of both sacroiliitis and spondylitis over either one on their own.
• Ankylosing spondylitis patients were more likely to have and report axial symptoms than patients with psoriatic spondyloarthritis.

Disclosures:

The study was funded through an unrestricted Investigator-Initiated Research grant by Pfizer Limited.

References:

Deepak R Jadon, Raj Sengupta, et al. "Axial Disease in Psoriatic Arthritis study: defining the clinical and radiographic phenotype of psoriatic spondyloarthritis," Annals of the Rheumatic Diseases. Published online Dec. 2, 2016. DOI: 10.1136/annrheumdis-2016-209853.