Background/Purpose: Patients with psoriasis and psoriatic arthritis (PsA) can develop a variety of comorbidities which may influence the therapeutic regimen and affect treatment results. Previous studies show a high incidence of coexistence of psoriasis and systemic lupus erythematosus (SLE). Unlike psoriasis, the coexistence of PsA and SLE has been reported only in case reports.

Objective:  To assess the prevalence of SLE in a PsA patient cohort and to compare it to the general population using the database of a large health care provider.

Methods: A retrospective database study consisting of a PsA cohort matched for age and sex with randomly selected control patients was conducted on patient data from 2002-2017, including demographics, clinical and laboratory manifestations of SLE and dispensed medications including  SLE-inducing drugs. Statistical analysis was conducted using Student’s t-test or Chi square test, as appropriate.  In the PsA group, incidence density sampling procedure (SAS v9.4) was performed matching PsA patients without co-existing SLE as controls to each case of PsA with co-existing SLE by age and follow-up time which was defined as date of SLE diagnosis.  Univariable and multivariable conditional logistic regression analysis were used to assess the influence of drugs, age at PsA diagnosis, PsA duration on development of SLE.  All tests were 2-sided; p values of < 0.05 were considered statistically significant.

Results: The PsA study group consisted of 4836 subjects, median age of 56+/-15, 2603 (53.8%) of whom were female. The control group consisted of 24180 subjects matched for age and sex.  Eighteen patients (0.37%) in the PsA study group and 39 patients (0.16%) in the control group where diagnosed with SLE (p=0.002). SLE patients without co-existing PsA had higher anti-double stranded DNA positivity (92.3% vs 66.7%, p=0.022) and positive anti-cardiolipin antibodies (46.2% vs 16.7%, p=0.041). No other significant differences were observed between the two groups in terms of SLE clinical and laboratory manifestations.  PsA patients with concomitant SLE compared to PsA patients without SLE were more often female (100% vs 53.7%, p< 0.0001), had more osteoporosis (38.9% vs 12.8%, p=0.005) and were more likely to be treated with beta blockers (27.8% vs 9.8% p=0.027). Usage of drugs with known potential to induce SLE prior to diagnosis of SLE was higher in the PsA than in the control group (11 out of 18 patients), but there was no difference in SLE manifestations between the groups.  Univariable and multivariable conditional logistic regression analysis showed that older age at PsA diagnosis (p=0.001, p=0.008, respectively), shorter PsA duration (p= 0.06, p=0.03) and statin treatment (p=0.01, p=0.012) were associated with SLE in PsA patients.

Conclusion: A 2.3 fold increase in the prevalence of SLE in PsA patients relative to control group was found in our study population. Risk factors for SLE development included older age at PsA diagnosis, shorter PsA duration, and statin treatment.  The positive correlates between SLE and PsA may point to common underlying pathogenetic pathways and may affect treatment choices and medication development.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/increased-prevalence-of-systemic-lupus-erythematosus-co-morbidity-in-patients-with-psoriatic-arthritis-a-population-based-case-controlled-study/