Hemophilia is a disease characterized by impaired blood clotting and the affected person is more prone to internal and external hemorrhages.
Patients with hemophilia A have alteration in the gene that codifies the factor VIII of blood clotting, a gene located in the non-homologous portion of the X chromosome. Patients with hemophilia B present a defect of the gene that codifies the factor IX of clotting, a gene also located in the non- homologous region of the X chromosome. Thus both diseases are X- linked diseases.