Hemophilia A is a hereditary blood coagulation (clotting) disorder. It is caused by a deficient activity of plasma protein factor VIII, which affects the clotting property of blood.
Causes, incidence, and risk factors
Hemophilia is a hereditary bleeding disorder of specific blood clotting factors. There are several types, including hemophilia A and B. Hemophilia A is the most common of these disorders and is the result of a deficiency of clotting factor VIII.
The disorder is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome. Thus, the disorder occurs primarily in males. Females carry two copies of the X chromosome, so if the factor VIII gene on one chromosome is defective, the gene on the other chromosome can compensate. Males, however, carry only one X chromosome, so if the factor VIII gene on that chromosome is defective, they will have the disease.
Females with one defective factor VIII gene are carriers of this trait. Fifty percent of the male offspring of female carriers have the disease and 50% of their female offspring are carriers. All female children of a male hemophiliac are carriers of the trait.
The severity of symptoms can vary with this disease, and the severe forms become apparent early on. Bleeding is the hallmark of the disease and sometimes, though not always, occurs if an infant is circumcised. Additional bleeding manifestations make their appearance when the infant becomes mobile.
Mild cases may go unnoticed until later in life when they occur in response to surgery or trauma. Internal bleeding may happen anywhere, and bleeding into joints is common. Risk factors are a family history of bleeding and being male.
Hemophilia A occurs in about 1 out of 5,000 men.
- Spontaneous bleeding
- Bleeding into joints and associated pain and swelling
- Gastrointestinal tract and urinary tract hemorrhage
- Blood in the urine or stool
- Prolonged bleeding from cuts, tooth extraction, and surgery
Signs and tests
Many blood clotting tests are performed if the person tested is the first one in the family to have a bleeding disorder. Once the defect has been identified, other family members will need less testing to diagnose the disorder.
- Prolonged PTT
- Normal prothrombin time
- Normal bleeding time
- Normal fibrinogen level
- Low serum factor VIII activity
Standard treatment is infusion of factor VIII 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.
Mild hemophilia may be treated with infusion of cryoprecipitate or desmopressin (DDAVP), which causes release of factor VIII that is stored within the body on the lining of blood vessels.
To prevent a bleeding crisis, people with hemophilia and their families can be taught to administer factor VIII concentrates at home at the first signs of bleeding. People with severe forms of the disease may need regular prophylactic infusions.
Depending on the severity of the disease, DDAVP or factor VIII concentrate may be given prior to dental extractions and surgery to prevent bleeding.
Immunization with Hepatitis B vaccine is necessary because of the increased risk of exposure to hepatitis due to frequent infusions of blood products.
Patients who develop an inhibitor to factor VIII may require treatment with other clotting factors such as factor VIIa, which can aide clotting even in the absence of factor VIII.
For additional resources, see hemophilia support group.
With treatment, the outcome is good. Most people with hemophilia are able to lead relatively normal lives. A small percentage of people with hemophilia will develop inhibitors of factor VIII, and may die from loss of blood.
- Chronic joint deformities, caused by recurrent bleeding into the joint, may be managed by an orthopedic specialist. These problems sometimes require joint replacement
- Recurrent transfusions may increase the risk of contracting HIV and hepatitis, especially prior to 1985 when blood screening procedures were improved for detecting the HIV virus. However, new heat processing treatment makes factor VIII material free of the HIV virus and thus safe for use.
- Intracerebral hemorrhage is another possible complication (see deep intracerebral hemorrhage, lobar intracerebral hemorrhage).
Calling your health care provider
- If symptoms of a bleeding disorder develops.
- (Call for screening) if a family member has been diagnosed with hemophilia A.
- If you have hemophilia A and you plan to have children.
- Genetic counseling
- Prenatal intrauterine diagnosis with termination of pregnancy as an option
by Gevorg A. Poghosian, Ph.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.