Haemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation. In its most common form, Hemophilia A, clotting factor VIII is absent. In Haemophilia B, factor IX is deficient. Hemophilia A occurs in about 1 in 5,000-10,000 male births, while Hemophilia B occurs at about 1 in about 20,000-34,000.
The effects of this sex-linked, X chromosome disorder are manifested almost entirely in males, although the gene for the disorder is inherited from the mother.