The 3 forms of hemophilia B
Classification is based on plasma activity levels of factor IX.
| Severity | Factor IX activity in plasma | Clinical signs |
|---|---|---|
| Severe | Factor IX < 1% (< 1 U/dL) | Spontaneous bleeding, mainly in joints and muscles |
| Moderate | 1% (1 U/dl) <= Factor IX < 5% (5 U/dL) |
Occasional spontaneous bleeding; serious bleeding in the event of trauma or surgery |
| Mild | 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 centers specializing in the treatment of hemophilia and involves administration of suitable products.