Spontaneous thrombosis in a patient with factor XI deficiency homozygous for the p.Cys398Tyr mutation.

Abstract

Factor XI (FXI) is a haemostatic plasma glycoprotein which circulates as a serine protease zymogen of activated FXI. It is essential for the generation of thrombin during coagulation. Abnormalities in its function or plasma levels are associated with the hereditary, rare bleeding disorder, FXI deficiency. FXI deficiency was first described in a Jewish family and the heterozygote frequency in the Ashkenazi Jewish population is 8%. FXI deficiency is associated with the genetic alterations in the F11 gene (4q35) encoding FXI. Homozygous or compound heterozygous subjects have severe FXI deficiency with FXI levels of less than 20 U/dL1.