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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
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 does not work, the gene on the other chromosome can do the job of making enough factor VIII.
Males have only one X chromosome. If the factor VIII gene is missing on a boy's X chromosome, he will have hemophilia A. For this reason, 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. Boys born to such women have a 50% chance of having hemophilia A. Their daughters have a 50% chance of being a carrier. All female children of men with hemophilia carry the defective gene. Risk factors for hemophilia A include:
The severity of symptoms vary. Bleeding is the main symptom of the disease. It is often first seen when an infant is circumcised. Other bleeding problems are seen when the infant starts crawling and walking.
Mild cases may go unnoticed until later in life. Symptoms may first occur after surgery or injury. Internal bleeding may occur anywhere.
Symptoms can include:
If you are the first person in the family to have a suspected bleeding disorder, your doctor will order a series of tests called a coagulation study. Once the specific defect has been identified, other people in your family will need tests to diagnose the disorder.
Tests to diagnose hemophilia A include:
Treatment includes replacing the missing clotting factor. You will receive factor IX concentrates. How much you get depends on:
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.
You should get the hepatitis B vaccine. People with hemophilia are more likely to get hepatitis because they may receive blood products. 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.
You can ease the stress of illness by joining a hemophilia support group. Sharing with others who have common experiences and problems can help you not feel alone.
With treatment, most people with hemophilia are able to lead a relatively normal life.
If you have hemophilia, you should have regular checkups with a hematologist.
Complications can include:
Call your health care provider if:
Carcao M, Moorehead P, Lillicrap D. Hemophilia A and B. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al., eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, Pa: Elsevier Saunders; 2012:chap 137.
Scott JP, Montgomer RR. Hereditary clotting factor deficiencies (bleeding disorders). In: Kliegman RM, Stanton BF, St. Geme JW III, et al., eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 470.
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