Hemophilia B is an inherited bleeding disorder, characterized by deficiency of factor IX activity, which interferes with proper clotting.  It occurs in approximately 1 in 20,000 newborn males worldwide.  Males are more commonly affected than females.  Hemophilia B is characterized by prolonged bleeding following an injury, surgery, or having a tooth extraction.  In severe cases of hemophilia B, spontaneous bleeding occurs after minor trauma or in the lack of injury.  Serious complications can arise from bleeding into internal organs, brain and muscles.  Milder forms of hemophilia can be noticed after surgery or a serious injury.  

Diagnosis can be confirmed by performing factor IX and PTT testing.  Approximately 10% of carrier females are at risk for bleeding.  Treatment for severe cases includes prophylactic infusions of factor IX concentrate to maintain factor IX clotting activity.

Mutations in the factor IX (F9) are responsible for hemophilia B.  This gene is located on the long arm of chromosome X.  The F9 gene codes for a protein called coagulation factor IX.  Coagulation factors play pivotal roles at the various stages of blood clotting.  After an injury, blood clots work effectively to prevent excessive blood loss.  Mutations in the F9 gene reduce the amount of the coagulation proteins.  As a result, blood clots cannot form properly in response to injury.