Christmas disease; Factor IX hemophilia
Definition of Hemophilia B
Hemophilia B is a hereditary bleeding disorder caused by a lack of blood clotting factor IX. Without enough factor IX, the blood cannot clot properly to control bleeding.
Causes, incidence, and risk factors
Hemophilia B is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome.
The severity of symptoms can vary, and the severe forms become apparent early on.
Signs and tests
If the patient is the first person in the family to have a suspected bleeding disorder, he or she will undergo a series of tests called a coagulation study. Once the specific defect has been identified, other family members will need less testing to diagnose the disorder.
Standard treatment is infusion of factor IX concentrates to replace the defective clotting factor. The amount infused depends upon the severity of bleeding, the site of the bleeding, and the size of the patient.
The outcome is usually good with treatment. Most people with hemophilia are able to lead relatively normal lives. A small number of people develop inhibitors of factor IX, and may die from loss of blood.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; James R. Mason, MD, Oncologist, Director, Blood and Marrow Transplantation Program and Stem Cell Processing Lab, Scripps Clinic, Torrey Pines, California. 3/28/10Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 3/28/2010