Factor XI deficiency
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.
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.