Hemophilia is a lifelong bleeding disorder that prevents blood from clotting properly. People with hemophilia do not have enough clotting factor, a protein in blood that controls bleeding. The severity of a person’s hemophilia depends on the amount of clotting factor that is missing.
A person with hemophilia does not bleed faster than anyone else, but bleeding may last longer. The main danger is uncontrolled internal bleeding that starts spontaneously or results from injury. Bleeding into joints and muscles can cause stiffness, pain, severe joint damage, disability, and sometimes death.