Disease-specific risk of venous thromboembolic events is increased in idiopathic glomerulonephritis

The risk of venous thromboembolic events is thought to be highest in patients with membranous nephropathy. This association has been recently questioned, and it is not known whether this simply reflects the severity of proteinuria. To better understand the relationship between histologic diagnosis and the risk of venous thromboembolic events we evaluated patients in the Toronto Glomerulonephritis Registry. Of 1313 patients with idiopathic glomerulonephritis, 395 were diagnosed with membranous nephropathy, 370 with focal segmental glomerulosclerosis (FSGS), and 548 with immunoglobulin-A nephropathy (IgAN). Risk factors were evaluated by Cox proportional hazards for 53 image-confirmed venous thromboembolic events in 44 patients during a median follow-up of 63 months. The risk was highest in patients with membranous nephropathy and FSGS (hazard ratios of 22 and 7.8, respectively) referenced to patients with IgAN. Following adjustment for gender, cancer history, proteinuria, and serum albumin by multivariable analysis, the histologic subtype remained an independent risk for venous thromboembolic events. This risk was still highest in patients with membranous nephropathy followed by FSGS with adjusted hazard ratios of 10.8 and 5.9, respectively. Thus, in this large cohort, histologic diagnosis was an independent risk factor for venous thromboembolic events. Further studies are needed to discover mechanisms responsible for this high risk in patients with membranous nephropathy.