Gender, clinical phenotype and imaging features of patients with late-onset psoriatic arthritis.

Objective: Psoriatic arthritis (PsA) is a chronic inflammatory disease affecting the musculoskeletal system. This study aimed to compare the gender, clinical and radiological characteristics between PsA patients with age of onset ≥ 50 years (late-onset) and patients with age of onset < 50 years (early-onset), and analyze the correlation between age onset and disease features.

Methods: A retrospective cohort study of 281 PsA patients from Peking University People's Hospital (2014-2022) was conducted. Demographic, clinical, laboratory, imaging and treatment data were collected. Comparisons between groups were performed using Student's t-test, Mann-Whitney U test and chi-square test. Logistic regression described the association between age of onset and disease characteristics.

Results: Among the 281 cases (207 early-onset vs74 late-onset), there were more female in the late-onset group and more male in the early-onset group (60.8% vs 39.2%, 53.1% vs 46.9%, P = 0.039). The onset of PsO was later (44.22 ± 3.79 vs 27.43 ± 1.45, P < 0.001) and duration from PsO to PsA was longer (17.39 ± 14.78 vs 8.37 ± 7.82, P < 0.05) in late-onset group. The late-onset group has a higher proportion of polyarthritis (66.7% vs 50.5%, P = 0.019) and comorbidities, but a lower proportion of psoriasis (89.2% vs 97.1%, P = 0.019). Besides, the late-onset patients presented higher levels of ESR, folate and tartaric acid phosphatase (trap-5b), but lower levels of hemoglobin and homocysteine. Imaging features revealed more frequent X-ray bone destruction (40.7% vs 25.3%, P = 0.033), synovitis (81.0% vs 62.6%, P = 0.01) and tenosynovitis under ultrasound (79.3% vs 56.8%, P = 0.002) in the late onset group.

Conclusions: Late-onset PsA was associated with a later onset of PsO, slower progression to PsA, and a higher frequency of peripheral polyarthritis and bone erosion. Age of onset is of great value in revealing the phenotypes and prognosis of PsA. Key Points • The age of onset plays a crucial role in the classification and prognosis of PsA. • The late onset of PsA is due to the delayed onset of PsO and the prolonged duration for PsO to progress into arthritis. • Late-onset PsA showed a greater tendency to develop bone erosion, particularly in peripheral joints, and to have comorbidities.