Autoimmune features in psoriatic arthritis

Objective: Psoriatic arthritis (PsA), traditionally classified as a seronegative spondyloarthropathy, is increasingly recognized to exhibit autoimmune characteristics. We aimed to investigate the prevalence of anti-nuclear antibody (ANA) and co-existing autoimmune diseases (co-AIDs), and assess their potential impact on clinical features in a real-life PsA cohort.Method: This retrospective, single-centre study included PsA patients followed at a tertiary university hospital between 2019 and 2024, classified according to CASPAR criteria. Demographic, clinical, and laboratory data, including co-AIDs, autoantibodies (when available), and disease activity scores, were obtained from medical records. Patients were stratified by ANA status and presence of co-AIDs. Statistical analyses were performed using chi-square/Fisher’s exact tests and t-test or Mann–Whitney U test and multivariable logistic regression models as appropriate, with a significance threshold of p < 0.05.Results: Among 219 PsA patients (62.1% female, mean age 45.8±12.4), 23.7% had at least one co-AID. The most common were autoimmune thyroid disorders (16.8%), followed by rheumatoid arthritis (2.3%), autoimmune hepatitis (0.9%), and antiphospholipid syndrome (0.9%). ANA positivity was observed in 35% of 100 tested patients; 72% had titres ≥1:100 and 57% showed a granular pattern. ANA-positive patients more frequently exhibited peripheral-predominant disease, though other clinical characteristics were similar. Co-AIDs were more common in females, obese patients, and those with a family history of rheumatic disease.Conclusion: In this real-world PsA cohort, co-AID frequency was found to be generally comparable to population rates, except for increased frequency of antiphospholipid syndrome and autoimmune hepatitis. ANA positivity was relatively common, though its clinical significance remains uncertain. Screening for autoimmune conditions may be considered in PsA patients, particularly women, those with obesity, and individuals with a rheumatic family history.