Hemophilia A is a hereditary bleeding disorder caused by a lack of blood clotting factor VIII. Without enough factor VIII, the blood cannot clot properly to stop bleeding.
Factor VIII deficiency
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.
If a woman has a defective factor VIII gene, she is considered a carrier. This means the defective gene can be passed down to her children. In a woman who carries the defective gene, any of her male children will have a 50% chance of having hemophilia A, while any of her female children will have a 50% chance of being a carrier. All female children of men with hemophilia carry the defective gene. Genetic testing is available for concerned parents.
Risk factors for hemophilia A include:
- Family history of bleeding
- Being male
Rarely, adults can develop a bleeding disorder similar to hemophilia A. This may happen after giving birth (postpartum), in people with certain autoimmune diseases such as rheumatoid arthritis, in people with certain types of cancer (most commonly lymphomas and leukemias), and also for unknown reasons (called "idiopathic"). Although these situations are rare, they can be associated with serious, even life-threatening bleeding.
The severity of symptoms vary. Bleeding is the main symptom of the disease and sometimes, although 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.
Symptoms may include:
- Bleeding into joints, with associated pain and swelling
- Blood in the urine or stool
- Gastrointestinal tract and urinary tract hemorrhage
- Prolonged bleeding from cuts, tooth extraction, and surgery
- Spontaneous bleeding
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.
Tests to diagnose hemophilia A include:
- Low serum factor VIII activity
- Normal prothrombin time
- Normal bleeding time
- Normal fibrinogen level
- Prolonged partial thromboplastin time (PTT)
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.
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 preventive treatment.
Depending on the severity of the disease, DDAVP or factor VIII concentrate may be given before having dental extractions or surgery in order to prevent bleeding.
Immunization with hepatitis B vaccine is necessary because of the increased risk of exposure to hepatitis due to frequent blood infusions.
Patients who develop an inhibitor to factor VIII may require treatment with other clotting factors such as factor VIIa, which can help with clotting even without any factor VIII.
For additional resources, see hemophilia support group.
The outcome is usually good with treatment. Most people with hemophilia are able to lead relatively normal lives.
Patients with hemophilia should establish regular care with a hematologist, especially one who is associated with a hemophilia treatment center. The ability to have quick and easy access to medical records documenting the patient's history of factor IX levels, factor transfusions (including the type and amount), complications, and amount of any inhibitors can be lifesaving in the event of an emergency situation.
Chronic joint deformities may occur from bleeding into joints. This complication can be managed by an orthopedic specialist. However, joint replacement may be needed.
Intracerebral hemorrhage is another possible complication.
Repeated transfusions may slightly raise the risk for HIV and hepatitis , however, continued improvements in blood screening procedures makes blood products safer than ever.
Calling your health care provider
Call your health care provider if:
- Symptoms of a bleeding disorder develops
- A family member has been diagnosed with hemophilia A
- You have hemophilia A and you plan to have children
- Genetic counseling
- Prenatal intrauterine diagnosis with termination of pregnancy as an option
Kessler CM. Hemorrhagic disorders: coagulation factor deficiencies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 180.