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FXI Deficiency

Heritable FXI deficiency is a rare bleeding disorder resulting from low functional levels of coagulation factor XI. Inheritance is autosomal. The estimated prevalence of major FXI deficiency (FXI:C ≤15 IU/dL) in most populations is about 1:1,000,000, however in Ashkenazi Jews it occurs in about 1:450 individuals.

Most bleeding in FXI deficiency is related to injury, although bleeding risk is unpredictable and not related to genotype. Some patients with major FXI deficiency do not bleed, others with partial FXI deficiency (FXI:C 16 to 60 IU/dL) may bleed.

Heritable FXI deficiency is caused by mutations in the factor XI gene (F11). Major FXI deficiency is generally associated with homozygosity or compound heterozygosity for F11 mutations. Partial FXI deficiency is usually associated with heterozygosity for mutations in F11. Genetic diagnosis has applications in family studies in FXI deficiency.