Hemophilia is a genetic bleeding disorder caused by insufficient levels of a blood protein required for normal blood clotting—clotting factor VIII in hemophilia A or clotting factor IX in hemophilia B. There are different degrees of severity of hemophilia, depending on the amount of clotting factor in the blood. People with mild hemophilia usually have problems with bleeding only after surgery, dental procedures, and trauma. People with moderate hemophilia may have occasional or frequent bleeding, depending on their clotting factor level. People with severe hemophilia may experience spontaneous joint and muscle bleeding, typically beginning at a very young age, and prolonged bleeding after injuries, traumas, and surgery. Hemophilia is considered a lifelong disease because the level of factor VIII or IX in the blood usually stays the same throughout a person’s life.^1-3

References:

1. https://rarediseases.org/rare-diseases/hemophilia-a/
2. https://rarediseases.org/rare-diseases/hemophilia-b/
3. https://elearning.wfh.org/elearning-centres/introduction-to-hemophilia/