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Hemophilia (A and B)
Wednesday, 02 July 2003
Monday, 29 November 2004

What

Hemophilia is a rare inherited blood clotting (also called coagulation) disorder caused by inactive or deficient blood proteins. The most common protein involved, called Factor VIII, is one of several proteins that enable the blood to clot. Hemophilia may be classified as mild, moderate, or severe. The level of severity is determined by the percentage of active clotting factor in the blood (normal percentage ranges from 50 to 150 percent). People who have severe hemophilia are extremely limited in the percent of active clotting factor in their blood. There are three major types of Hemophilia, but the two of interest here are: Hemophilia A (also known as classical hemophilia, Factor VIII deficiency or antihemophilic globulin [AHG] deficiency); and Hemophilia B (Christmas disease or factor IX deficiency). Both types of hemophilia are indistinguishable by the doctor without special blood tests.

Who

The prevalence of Hemophilia A in the United States is 20.6 cases per 100,000 males, with 60% of those having severe disease. The prevalence of Hemophilia B is 5.3 cases per 100,000 males, with 44% of those having severe disease.

Signs and Symptoms

Bruising Spontaneous Bleeding Bleeding into joints, with associated pain and swelling Blood in urine or feces Prolonged bleeding from cuts, tooth extraction, and surgery Nosebleeds (Hemophilia B)

Possible Causes

Hemophilia A and B are inherited, in an X-linked recessive pattern. In other words, if the gene that expresses the protein is missing or defective in the X-chromosome (one found in males and two are found in females), hemophilia will result. Therefore, there is an increased likelihood that Hemophilia A or B will be expressed in males because they only have one X-chromosome containing the missing or defective gene that will lead to the condition. In females, however, one missing or defective X-chromosome may be compensated by a second, normal, X-chromosome. Female hemophiliacs are possible through a process known as lyonization (inactivation of one of the X chromosomes).

Diagnosis

A Partial thromboplastin time or activated partial thromboplastin (PTT or APTT) is performed. The test requires that blood be drawn in order to measure how long the sample takes to completely clot inside the test tube. A prolonged PTT time indicates hemophilia. Normal bleeding time. In this procedure a small superficial cut is made and the duration of bleeding is measured. Since this test measures the ability of the platelets, not coagulation factors, to form a temporary seal at the injury site, bleeding time should, therefore, be normal and not affected by the hemophilia. Prothombin time should be normal since this test measures clotting time after Thrombin, a major blood clotting protein, is added. Clinicians also measure fibrinogen (the precursor protein that actually forms the clot) levels. Fibrinogen levels should be normal since hemophiliac patients are missing proteins that convert fibrinogen into an active clotting protein. Low serum factor VIII activity (low factor IX in Hemophilia B).

Treatment

Standard treatment is infusion (intravenous application) of factor VIII or IX (hemophilia A or B) 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. Hepatitis B vaccine is recommended for individuals with Hemophilia B because they are at increased risk of developing hepatitis due to exposure to blood products. To prevent a bleeding crisis, people with hemophilia and their families can be taught to administer factor IX concentrates at home at the first signs of bleeding. People with severe forms of the disease may need regular preventative infusions. Depending on the severity of the disease, factor VIII or IX concentrate may be given prior to dental extractions and surgery to prevent bleeding. Sometimes another medicine(Amikar) that prevents the breakdown of fibrinogen (another important clotting protein) is used with factor replacement.

Prognosis

The outcome looks good with treatment. Most people with hemophilia are able to lead relatively normal lives. A small percentage of people develop inhibitors of factor VIII and IX making replacement therapy more challenging.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

National Hemophilia Foundation (NHF)
A great website with information about Hemophelia and about ongoing esearch. There is also educational material and links to support groups and other support events.

Canadian Hemophilia Society
A comprehensive, easy to navigate website about hemophilia, including research.

Medline Plus
A nice summary of hemophilia with nice definitions of medical terms.

Google Search for Hemophilia (A and B)

References and Sources

www.rarediseases.org www.nlm.nih.gov/medlineplus/medlineplus.html www.emedicine.com www.hemophilia.org