Hemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation, which is used to stop bleeding when a blood vessel is broken.
Hemophilia A is the most common type of this condition, affecting 1 in 5,000 to 10,000 males worldwide. Hemophilia B is less common; it affects 1 in 20,000 to 34,500 males worldwide.