Although congenital deficiencies of the natural anticoagulant proteins antithrombin, protein C and protein S are present altogether only in approximately 1/1000 individuals in the general population [14], one should bear in mind that these proteins can selectively decrease in plasma during the relapse of nephrotic syndrome, and therefore contribute to increase the risk of venous thrombosis. The gene discussed is PROS1; the disease is nephrotic syndrome.