Tests & Clinical Applications, Hemophilia B, What are the clinical signs?

The 3 forms of hemophilia B

Classification is based on plasma activity levels of factor IX.


Factor IX activity in plasma

Clinical signs


Factor IX < 1% (< 1 U/dL)

Spontaneous bleeding, mainly in
joints and muscles


1% (1 U/dl) <= Factor IX
< 5% (5 U/dL)

Occasional spontaneous bleeding;
serious bleeding in the event of
trauma or surgery


5% (5 U/dL) <= Factor IX
 =< 40% (40 U/dL)

Serious bleeding in the event of trauma or surgery

Special features of the severe forms

Severe forms of hemophilia B are associated with the most serious hemorrhagic signs. These can appear after seemingly innocuous trauma that often go unnoticed and such episodes are thus referred to as spontaneous hemorrhages. There is a high risk of hemorrhage in the event of surgery.
Severe hemophilia B occurs in 30 to 40% of cases.

The most common hemorrhagic episodes consist of:

  • hemarthrosis: 70%,
  • subcutaneous or intramuscular hematomas: 10 to 20%,
  • hemorrhaging in the urinary tract, nasal and gastrointestinal mucosa, and intra-abdominal organs: 10 to 20%

Gastrointestinal and central nervous system hemorrhagic accidents are potentially life-threatening, while others such as bleeding in the orbit, the front of the forearm or the axilla may compromise function. Emergency treatment is required at centres specialising in the treatment of hemophilia and involves administration of suitable products.