Venous thromboembolism in patients with lupus nephritis: frequency and risk factors—a cohort study

Objectives Venous thromboembolism (VTE) is a known complication of systemic lupus erythematosus (SLE), yet there is a lack of high-quality studies specifically focused on lupus nephritis (LN). This study aimed to assess the frequency of VTE in patients with LN and identify risk factors for its development. Methods We included patients with biopsy-proven LN from a prospective observational cohort followed between 1970 and 2024. The primary outcome, VTE occurring after the onset of LN, was monitored longitudinally, and the time to the first event was calculated. Time-varying univariable and multivariable cause-specific Cox proportional hazards models were used to identify factors associated with the first VTE, with death considered a competing risk. Results A total of 324 patients were included, with a mean age of 34.2 years [IQR: 25.9–43.0] at LN onset. Over a long-term follow-up period of 9.9 years [IQR: 5.0–16.4], 30 patients (9.3%) developed VTE, with a total of 34 events. The median time to the first event from LN onset of 4.4 years [IQR, 0.1, 14.1]. Most events were isolated (86.7%), including 19 deep vein thromboses (DVTs, 59.4%), 5 pulmonary embolisms (PEs), and 2 events involving other venous beds. In the multivariable model, the following factors were independently associated with the development of VTE: the SLEDAI-2K score (HR = 1.05, 95% CI: 1.01–1.10) and proteinuria level (HR = 1.26, 95% CI: 1.08–1.47). Conclusions VTE can complicate the course of LN at any stage. Disease activity and proteinuria are the primary risk factors for its development.