It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to haemophilia.

[9] Factors VII, IX, and X all play key roles in blood coagulation and also share a common domain architecture.

[10] Wilkinson et al. conclude that residues 88 to 109 of the second EGF domain mediate binding to platelets and assembly of the factor X activating complex.

Because the gene for factor IX is located on the X chromosome (Xq27.1-q27.2), loss-of-function mutations thereof are X-linked recessive: males experience the disease phenotype much more frequently than females.

[16] Polly, a transgenic cloned Poll Dorset sheep carrying the gene for factor IX, was produced by Dr Ian Wilmut at the Roslin Institute in 1997.

Tranexamic acid may be of value in patients undergoing surgery who have inherited factor IX deficiency in order to reduce the perioperative risk of bleeding.