Radiographic Sacroiliitis Progression in Psoriatic Arthritis

Objective To assess radiographic sacroiliitis progression in psoriatic arthritis (PsA) and factors associated with it. Methods We analyzed a prospective PsA cohort (1978–2025). Pelvic radiographs were obtained biannually. Change (Δ) in the Sacroiliitis Sum Score (SSS, 0–8; left+right modified New York–mNY—grades) was the primary outcome, while patients with SSS = 8 at baseline were excluded from the analyses. Linear mixed-effects models assessed factors associated with ΔSSS over successive clinic visits. As a secondary outcome, time to incident mNY sacroiliitis was evaluated with Cox regression. Results Among 1,554 eligible patients (median follow-up 6.00 years), 475/1,056 (45%) showed progression in SSS by at least 1 grade. In univariable analyses, male sex, 66-joint swollen count, PASI, nail disease, syndesmophytes, abnormal ESR/CRP and higher DAPSA were associated with progression, while older age and longer PsA duration were associated with less progression. Biologic/targeted synthetic (b/ts) DMARD exposure and follow-up in the post-2011 era were associated with lower progression rates. In multivariable models, older age and b/tsDMARD exposure retained protective associations. Among 831 patients without definite mNY sacroiliitis at baseline and with ≥1 follow-up radiograph, 189 (22.7%) developed definite mNY sacroiliitis. In univariable Cox analysis, nail disease, higher PASI, abnormal ESR/CRP, higher DAPSA, and syndesmophytes were associated with progression, while b/tsDMARD exposure and later eras were associated with lower progression; effects were attenuated after adjustment. Conclusion Radiographic sacroiliitis progression is common in PsA. Greater inflammatory activity increased risk, whereas b/tsDMARD exposure were protective; progression was lower in the modern treatment era.