Molecular characterization of FXI deficiency.

Factor XI (FXI) deficiency is a rare autosomal bleeding disease associated with genetic defects in the FXI gene. It is a heterogeneous disorder with variable tendency in bleeding and variable causative FXI gene mutations. It is characterized as a cross-reacting material-negative (CRM-) FXI deficiency due to decreased FXI levels or cross-reacting material-positive (CRM+) FXI deficiency due to impaired FXI function. Increasing number of mutations has been reported in FXI mutation database, and most of the mutations are affecting serine protease (SP) domain of the protein. Functional characterization for the mutations helps to better understand the molecular basis of FXI deficiency. Prevalence of the disease is higher in certain populations such as Ashkenazi Jews. The purpose of this review is to give an overview of the molecular basis of congenital FXI deficiency.