Greater Entheseal Damage, Inflammation Observed in Psoriatic Arthritis vs Ankylosing Spondylitis
Data suggest potential differences in tissue repair, immunobiology, or response to injury at insertions.
Patients with psoriatic arthritis (PsA) sustain greater inflammation at entheseal sites compared with patients with ankylosing spondylitis (AS), according to study data published in Rheumatology.
Patients with PsA (n=85) and AS (n=79) underwent ultrasound scans for 1640 total entheses. Ultrasound findings were quantified in part by an inflammation score, which was calculated as the sum of hypoechogenicity, thickening, and entheseal Doppler scores. An additional damage score was obtained from the sum of calcification, erosions, and enthesophytes. Regression modeling was performed to evaluate the effect of each respective diagnosis on inflammation and damage outcomes. Additional demographic and clinical factors included age, sex, body mass index (BMI), diagnosis of clinical enthesitis, human leukocyte antigen B27 (HLA-B27) positivity, and use of anti-tumor necrosis factor (anti-TNF) drugs.
Patients with PsA were older (P <.005), had higher BMI (P =.021), were more likely to be women (P <.001), and had a lower frequency of HLA-B27 positivity and anti-TNF use (both P <.001) compared with patients with AS. Patients with PsA had significantly higher damage scores (P =.008) and numerically higher inflammation scores (P =.077) compared with patients with AS. HLA-B27 positivity was associated with increased inflammation (P <.001) and damage (P =.03) scores across all patients. In addition, inflammation scores were positively correlated with BMI (P <.001), disease duration (P =.017), and age (P <.001), whereas damage scores were positively correlated with BMI and age only (both P <.001).
Anti-TNF therapies were found to have a negative correlation with inflammation scores, although not at a statistically significant threshold (P =.083). Among individuals who were not using anti-TNF medication, significant differences were observed between patients with PsA and AS. Specifically, women with PsA had 5% less inflammation than women with AS. A similar effect was observed for men, but the association was not statistically significant. In addition, a significant effect was observed between diagnosis and age (P <.001) with respect to damage scores: patients with PsA had 4.22 times more ultrasound damage than their age-matched counterparts.
These data highlight the sonographic differences in entheses between patients with PsA and AS. Further research is necessary to identify the mechanisms behind these differences. Clinicians may find these data useful in designing treatment plans for patients with PsA whose clinical or demographic profiles place them at high risk for entheseal inflammation or damage.
Alhussain FA, Gunal EK, Kurum E, et al. Greater magnitude of entheseal microdamage and repair in psoriatic arthritis compared with ankylosing spondylitis on ultrasound [published online September 26, 2018]. Rheumatology. doi: 10.1093/rheumatology/key238