Exome Sequencing and Clot Lysis Experiments Demonstrate the R458C Mutation of the Alpha Chain of Fibrinogen to be Associated with Impaired Fibrinolysis in a Family with Thrombophilia

Aim: We report the study of a familial rare disease with recurrent venous thromboembolic events that remained undiagnosed for many years using standard coagulation and hemostasis techniques. Methods: Exome sequencing was performed in three familial cases with venous thromboembolic disease and one familial control using NimbleGen exome array. Clot lysis experiments were performed to analyze the reasons of the altered fibrinolytic activity caused by the mutation found. Results: We found a mutation that consists of a R458C substitution on the fibrinogen alpha chain (FGA) gene confirmed in 13 new familial subjects that causes a rare subtype of dysfibrinogenemia characterized by venous thromboembolic events. The mutation was already reported to be associated with a fibrinogen variant called fibrinogen Bordeaux. Clot-lysis experiments showed a decreased and slower fibrinolytic activity in carriers of this mutation as compared to normal subjects, thus demonstrating an impaired fibrinolysis of fibrinogen Bordeaux. Conclusions: The exome sequencing and clot-lysis experiments might be powerful tools to diagnose idiopathic thrombophilias after an unsuccessful set of biochemical laboratory tests. Fibrinogen Bor-deaux is associated with impaired fibrinolysis in this family with idiopathic thrombophilia.