Hemophilia A

Definition

Hemophilia A is a hereditary bleeding disorder caused by a lack of the blood clotting factor VIII. 

Causes, incidence, and risk factors

Hemophilia A results from a deficiency (lack) of clotting factor VIII.

The disorder is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome. That means the disorder occurs primarily in males. Females carry 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. Males, however, carry only one X chromosome, so if the factor VIII gene on that chromosome is broken, they will have hemophilia A.

If a woman has a defective factor VIII gene, she is considered a carrier. The gene can be passed down to her children. Half of the male babies born from women who carry the defective gene have the disease. Half of the female babies born from women who have the defective gene are carriers. All female children of men with hemophilia carry the defective gene. 

The severity of symptoms can vary. Severe forms become apparent early on. Bleeding is the main symptom of the disease and sometimes, though not always, occurs if an infant is circumcised. Additional bleeding problems are seen when the infant starts crawling and walking.

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.

Symptoms

• Bruising
• 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.

Tests include:

• Prolonged PTT
• Normal prothrombin time
• Normal bleeding time
• Normal fibrinogen level
• Low serum factor VIII activity

Treatment

Standard treatment involves replacing the missing clotting factor. The amount of factor VIII concentrates needed depend upon the severity of bleeding, the site of the bleeding, and the size of the patient.

Mild hemophilia may be treated with desmopressin (DDAVP), which helps the body release factor VIII that is stored within the lining of blood vessels.

To prevent a bleeding crisis, people with hemophilia and their families can be taught to give factor VIII concentrates at home at the first signs of bleeding. People with severe forms of the disease may need regular preventative treatment.

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.

Support Groups

For additional resources, see hemophilia support group.

Expectations (prognosis)

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.

Complications

• 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

Prevention

• Genetic counseling
• Prenatal intrauterine diagnosis with termination of pregnancy as an option

Illustrations

Blood clots

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