Increased prevalence of systemic lupus erythematosus comorbidity in patients with psoriatic arthritis: A population-based case-control study

Objective: To assess the prevalence of systemic lupus erythematosus (SLE) in a psoriatic arthritis (PsA) cohort and to compare it to the general population using the database of a large healthcare provider. Methods. We analyzed the database of a PsA cohort (2002-2017), matched for age and sex, with randomly selected controls for demographics, clinical and laboratory manifestations, and dispensed medications. Statistical analysis used t test and chi-square test as appropriate. In the PsA group, incidence density sampling was performed matching PsA patients without SLE as controls to each case of PsA with SLE by age and follow-up time. Univariable and multivariable conditional logistic regression analyses were used to assess factors affecting SLE development. Results. The PsA and control groups consisted of 4836 and 24,180 subjects, respectively, with a median age of 56 ± 15 years, and of whom 53.8% were female. Eighteen patients (0.37%) in the PsA group and 36 patients (0.15%) in the control group were diagnosed with SLE (P = 0.001). SLE patients without PsA had higher anti-dsDNA and anticardiolipin antibodies. The usage of drugs with known potential to induce SLE was higher in the PsA than in the control group. Older age at PsA diagnosis, shorter PsA duration, and statin treatment were associated with SLE in PsA patients. Conclusion. A 2.3-fold increase in the prevalence of SLE in PsA relative to the control group was found. Risk factors for SLE development included older age at PsA diagnosis, shorter PsA duration, and statin treatment. The association between PsA and SLE may affect treatment choices and medication development.