Cutaneous lupus erythematosus and the risk of deep venous thrombosis and pulmonary embolism: A Danish nationwide cohort study

Background Venous thromboembolism (VTE) is a major public health concern. Lupus erythematosus (LE) is a chronic autoimmune disease ranging from localized cutaneous disease (CLE) to systemic involvement (SLE). Patients with SLE have an increased risk of venous thromboembolism (VTE), but little is known about the CLE-related risk of VTE. Methods To evaluate the risk of VTE in patients with SLE and CLE as compared to the general population, a retrospective cohort study was conducted. Incidence rates and hazard ratios (HRs) with 95% confidence intervals (CIs) from multivariable Cox regression models were used to evaluate and compare the risk of VTE. Registries of hospitalizations, outpatient visits, and prescription drug use were studied to determine the risk of VTE in patients with CLE and SLE and the general population between 1997 and 2011. Results A total of 3234 patients with CLE and 3627 patients with SLE were identified and compared to 5,590,070 individuals in the reference population. The incidence rates per 1000 year of VTE were higher in patients with LE, i.e. 1.20, 3.06, and 5.24 for the reference population, CLE, and SLE, respectively. In adjusted models, both CLE (HR 1.39; 95% CI 1.10-1.78) and SLE (HR 3.32; 95% CI 2.73-4.03) were associated with a statistically significant increased risk of VTE, compared to the reference population. Conclusion In this nationwide study, both CLE and SLE were significant risk factors for VTE. The results add to our understanding of comorbidities in patients with LE, and call for further studies and increased awareness of thromboembolic complications in patients with CLE.