The factor V Leiden mutation and risk of renal vein thrombosis in patients with nephrotic syndrome

Abstract

Background: Acquired abnormalities of coagulation and fibrinolysis in nephrotic syndrome have been implicated in the pathogenesis of renal vein thrombosis (RVT). Whether resistance to activated Protein C due to a mutation in the gene for factor V (FV Leiden/FV506Q, the commonest inherited risk factor for venous thrombosis) could contribute to risk of RVT in patients with nephrotic syndrome is unknown. Methods: Genotyping for the factor V Leiden mutation was undertaken in a retrospective study of 35 patients with a history of nephrotic syndrome, 10 of whom had suffered clinically significant and radiologically proven RVT. Results: Two patients (6%) were heterozygous for the FV506Q mutation, a prevalence similar to studies within the general population. One heterozygote had suffered a RVT, whilst the other without a native RVT subsequently had a primary renal allograft thrombosis. Conclusions: In a retrospective study the prevalence of the FV Leiden mutation was not increased in patients with nephrotic syndrome nor associated with prevalence of clinically significant RVT. Whilst this study was insufficiently powerful to fully exclude an association, it suggests acquired rather than inherited alterations in the coagulation/fibrinolytic balance associated with nephrosis may be of greater importance in venous thrombotic risk, and that routine screening of patients with nephrosis for this mutation will not identify the majority of patients at risk for RVT. Confirmation of these results and determining whether the natural history of thrombosis or underlying renal disease in carriers of the FV Leiden mutation differs from those without this mutation, will require a large prospective study.