- Hemophilia A and B are X-linked transmitted disorders characterized by a lack of coagulation factor VIII (FVIII) or coagulation factor IX (FVIII), respectively, or by antibodies against FVIII or FIX.
- Although females may carry a trait, with very mild clinical signs, hemophilia A is mainly found in males.
- Severe hemophilia (factor activity <1%) is associated with severe spontaneous bleeding into major joints (elbows, knees and ankles) leading to hemarthroses, intramuscular bleeding, and retroperitoneal bleeding.
- Moderate hemophilia (factor activity 1% – 5%) is associated with less significant bleeding.
- Mild hemophilia (factor acitivity >5% – <40%) usually only manifests as impaired hemostasis after severe trauma or surgical procedures.
- Total joint replacements are not uncommon in patients with severe hemophilia.