A case of factor X (FX) deficiency due to novel mutation V196M, FX Hofu

The patient, a 20-year-old male, was found to have a slightly prolonged prothrombin time (PT). No episodes of bleeding were noted. The measurement of coagulation factors revealed that the level of factor X (FX) activity was solely deficient, 51% (normal range: 70–130% ), and that of FX antigen was 100%. Analysis of the entire FX gene revealed the novel missense mutation of GTG to ATG, resulting in the substitution of the 196th amino acid valine → methionine. The mother and younger brother had a normal PT time and expressed no episode of bleeding. The mother exhibited a normal level of FX activity and antigen; however the younger brother showed a slight decrease in both the parameters. This mutation was not observed in the mother and younger brother. Polymorphism is not observed at this point in healthy persons. The present novel FX mutation was named FX Hofu.