Hemophilia : Genes

by Food and Drug Administration (FDA)

(Page 3 of 3)

Tailoring Care

A person with hemophilia lacks one of the dozen or so factors that cause blood to clot. In hemophilia A, factor VIII is at fault; in hemophilia B, it's factor IX. Treatment consists of intravenous infusion of the missing factor and is now usually done at home. When and how much antihemophilic factor patients need depends on the severity of their disease. In severe hemophilia, clotting factor activity is less than 1 percent of normal. Injury, surgery, or dental care can present significant problems requiring treatment. Spontaneous bleeding can require infusion of factor concentrate as often as several times a week in severe hemophilia.

People with factor levels between 1 and 5 percent of normal (moderate hemophilia) don't usually experience spontaneous bleeds, but even a minor injury, if untreated, can cause prolonged bleeding.

In mild hemophilia, factor activity ranges between 5 and 50 percent of normal. Bleeding can be expected from surgery, major dental care, or trauma. But these individuals rarely bleed into joints, and their disease usually doesn't interfere with normal living.

The physician determines how much factor should be infused when bleeding is detected. Early signs of internal bleeding include a bubbling or tingling sensation or a feeling of warmth, tightness, or stiffness in the affected area. Following a blow to the head, headache, confusion, drowsiness, or other evidence of neurological impairment may signal internal bleeding. Caregivers of infants and toddlers need to watch for signs of joint or muscle pain caused by internal bleeding. The child may cry for no apparent reason, refuse to use an arm or leg, refuse to walk, or have swelling or excessive bruising. Patients old enough to care for themselves are taught to inject clotting factor when they need it. Manufacturers supply antihemophilic products in kits designed for home use, and the physician advises each patient how many units of factor to administer when a bleed occurs.

Patients who have an immune reaction that makes factor VIII ineffective in controlling bleeding may be helped by a factor product from pig's plasma or a product (prothrombin complex concentrate) that can induce clotting despite the lack of normal factor VIII. A hormone, desmopressin, has also been used successfully to control bleeding in hemophilia patients undergoing surgical and dental procedures. Hemophilia treatment is costly. A year's treatment with one of the recombinant DNA products for a person with severe hemophilia (70 percent of patients) can cost $70,000 or more. Physician visits, laboratory testing, and other health-care expenses can easily push the cost of treating severe hemophilia to $100,000 a year, says the National Hemophilia Foundation.

People who want more information about hemophilia care and the location of comprehensive treatment centers throughout the country can contact the National Hemophilia Foundation, 110 Greene St., Suite 303, New York, NY 10012, telephone [phone]. Information on dealing with AIDS in the hemophilia community is available from HANDI (Hemophilia and AIDS/HIV Network for Dissemination of Information), operated by the Hemophilia Foundation. The toll-free number is (1-800) 42HANDI or [phone].

It's in the Genes

The genes responsible for producing factors VIII and IX were isolated in 1984. They are located on the X chromosome, one of the pair of chromosomes that determines gender. Females have two X chromosomes; males have one X and one Y chromosome. Female carriers of hemophilia have one normal and one defective X chromosome. They don't develop symptoms of the disease because the normal X chromosome contains genes that tell the body how to produce factors in quantities sufficient to control bleeding. But if a hemophilia carrier passes the abnormal X chromosome to her son, he will have hemophilia.

Hemophilia itself can occur in females, but it is extremely rare. If the father has hemophilia and the mother is a carrier, their daughters have a 50/50 chance of inheriting a defective X chromosome from each parent. If a girl is born with only one functioning X chromosome and it is defective, she can develop hemophilia.

About a third of people with hemophilia are born to women with no known family history of the disease — apparently the result of a spontaneous mutation rather than heredity. But here too the problem is defective genes on the X chromosome.

The National Hemophilia Foundation estimates that nearly 450 babies with hemophilia are born each year in the United States — 1 in every 4,400 live male births. The number of female hemophiliacs is not known.

About the Author

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