Structural entheseal lesions in patients with psoriasis are associated with an increased risk of progression to psoriatic arthritis

Objective To test whether the presence of structural entheseal lesions in psoriasis patients influences the risk for the progression to psoriatic arthritis (PsA). Methods Prospective cohort study on psoriasis patients without clinical evidence of musculoskeletal involvement receiving baseline assessment of structural entheseal lesions and volumetric bone mineral density (vBMD) at entheseal and intra-articular sites by high-resolution peripheral quantitative computed tomography (HR-pQCT). Adjusted relative risks of developing PSA associated with baseline volumetric bone density and the presence of structural entheseal lesions were calculated using multivariable Cox regression models. Results The cohort included 114 psoriasis patients (M/F 72/42) with a mean (SD) follow-up duration of 28.2 (17.7) months, during which 24 patients developed PsA (9.7 /100 patient-years, 95%CI 6.2 to 14.5). Patients with structural entheseal lesions were at higher risk of developing PsA compared to patients without such lesions (21.4/100 patient-years, 95%CI 12.5 to 34.3, HR 5.10, 95%CI 1.53 to 16.99, p=0.008). With respect to vBMD, a 1-standard deviation increase in entheseal, but not intra-articular vBMD was associated with an approximate 30% reduced risk to progress to PsA. Especially, higher cortical vBMD at entheseal segments was associated with a lower risk of developing PsA (HR 0.32 per SD, 95%CI 0.14 to 0.71), and remained robust after multiple imputation of missing data (HR 0.64, 95%CI 0.42 to 0.98). Conclusion Presence of structural entheseal lesions as well as low cortical vBMD at entheseal segments are associated with an increased risk of developing PsA in patients with psoriasis.