Hemophilia is a bleeding disorder in which the blood does not clot properly. This bleeding disorder is usually inherited, however, in 30% of cases, there is no family history of hemophilia.

Blood contains many proteins called clotting factors that help to stop bleeding. People with hemophilia have low levels of either factor VIII (8) or factor IX (9), referred to as hemophilia A and B respectively. The deficiency of one of these factors can lead to spontaneous bleeding in muscles, organs, and joints, as well as prolonged bleeding following injuries or surgery.

In a person affected by hemophilia, the level of severity is determined by the amount of clotting factor in the blood and is described as mild, moderate, or severe.

Hemophilia affects roughly 20,000 individuals in the United States.