Factor XI Deficiency
OMIM Link for Factor XI Deficiency
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Clinical Features of Factor XI Deficiency
Factor XI deficiency was originally identified as hemophilia C by Rosenthal and coworkers in 1953. Deficiency in factor XI is inherited as an autosomal condition with clinical manifestations seen in both homozygotes and heterozygotes. Twenty distinct mutations and deletions have been identified in patients suffering from factor XI deficiency all of which are associated with low levels of factor XI and low activity. Most of the mutations, as well as afflicted individuals, are of Jewish with the first patients identified being of Ashkenazi Jewish descent. The frequency of this disorder in Ashkenazi Jewish persons in as high as 1 in 190. Bleeding tendency in factor XI deficient patients is less severe and much more variable than in hemophila A or hemophilia B.
Bleeding in factor XI deficiency is most often triggered by surgery or trauma. Spontaneous bleeding, as occurs in both hemophilia A and B, is very rare in factor XI deficiency. Excessive bleeding from sites of injury can persist for several hours to days. However, there is a variability to the severity of bleeding where some individuals with levels of factor XI that are <1% of normal do not bleed excessively despite trauma. This phenotypic phenomenon is the result of both the inherited genotype as well as the site of injury. Bleeding due to surgery or trauma on tissues with a high fibrinolytic, such as the oral cavity, is the most severe.
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Michael W. King, Ph.D / IU School of Medicine / miking at iupui.edu