Definition of Hemophilia A
Hemophilia A is a hereditary caused by a lack of blood clotting factor VIII. Without enough factor VIII, the blood cannot clot properly to stop bleeding.
Causes, incidence, and risk factors
Hemophilia A is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome. Females have two copies of the X chromosome, so if the factor VIII gene on one chromosome doesn’t work, the gene on the other chromosome can do the job of making enough factor VIII. Males, however, have only one X chromosome, so if the factor VIII gene on that chromosome is defective, they will have hemophilia A. Thus, most people with hemophilia A are male.
The severity of symptoms vary. Bleeding is the main symptom of the disease and sometimes, although not always, occurs if an infant is circumcised.
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 a disorder has been identified, other family members will need less testing to diagnose the disorder.
Standard treatment involves replacing the missing clotting factor. The amount of factor VIII concentrates needed depends on the severity of the 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.
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. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 3/28/2010