To understand whether psoriasis has disease modifying effects on disease features and/or severity of enthesitis and spine disease in axial SpA (axSpA).
Patients with a diagnosis axSpA were included. Demographics, patient and physician reported outcomes were collected. Radiographic damage in the spine was assessed using modified Ankylosing Spondylitis Spine Score (mSASSS). Twelve entheses of the upper and lower extremity were assessed using ultrasound, focusing on inflammation and damage separately. The association between mSASSS, enthesitis scores and extra-articular manifestations such as psoriasis was analyzed using linear regression analysis.
Among 120 axSpA patients 114 (95%) had axSpA according to The Assessment of SpondyloArthritis international Society (ASAS) criteria. Sixty-two were classified as ankylosing spondylitis (AS), fulfilling the modified New York criteria. Thirty-one patients had psoriasis. For spinal damage, entheseal damage was an independent and the strongest predictor (B = 0.52, p = 0.025), in addition to longer disease duration (B = 0.22, p = 0.045) and male gender (B = 6.1, p = 0.041) but not psoriasis. For enthesitis, psoriasis was found as an independent risk factor to increase the entheseal damage (B = 4.38, p = 0.009), in addition to age (B = 0.17, p = 0.007), male gender (B = 2.8, p = 0.032), mSASSS (B = 0.11, p = 0.035) and body mass index (B = 0.57, p < 0.001), but not entheseal inflammation (B = 2.0, p > 0.05) when corrected for HLA-B27.
Psoriasis is an independent risk factor to increase the severity of entheseal damage, but not spinal damage. Peripheral enthesitis predicts spinal damage, regardless of the subtypes of SpA.