Factor XI deficiency causes a type of bleeding disorder known as a hemophilia, in this case, hemophilia C.
More than 150 mutations that can cause hemophilia are known to occur in the gene for blood clotting factor XI. About 1 in 23 Ashkenazi Jews carries one of three relatively common factor XI mutations. Carriers usually do not develop overt disease, however, the relationship between the amount of factor XI in a person's blood and the severity of any symptoms is unclear. People with only a mild deficiency in factor XI can have serious bleeding episodes, and the symptoms can vary widely, even among family members.[1]
23andMe tests for the following SNPs associated with factor XI deficiency:
- rs373297713 or i4000397, also known as IVS14-1G>A (risk genotype AA)
- rs121965063 or i4000398, also known as E117X (risk genotype TT)
- rs121965064 or i4000399, also known as F283L (risk genotype CC). This mutation is found only among Ashkenazi Jews. People with two copies of this SNP appear to have a relatively lower risk of bleeding after injury.
