What Is Hemophilia

What Is Hemophilia?

Hemophilia (heem-o-FILL-ee-ah) is a rare, inherited bleeding disorder in which your blood doesn’t clot normally. If you have hemophilia, you may bleed for a longer time than others after an injury. You also may bleed internally, especially in your knees, ankles, and elbows. This bleeding can damage your organs or tissues and, sometimes, be fatal.

People born with hemophilia have little to none of a protein needed for normal blood clotting. The protein is called a clotting factor. There are several types of clotting factors, and they work together with platelets to help the blood clot. Platelets are small pieces of blood cells that are formed in the bone marrow. They play a major role in blood clotting.

When blood vessels are injured, clotting factors help the platelets stick together to plug cuts and breaks at the site of the injury to stop the bleeding. Without clotting factors, normal blood clotting can’t take place. Sometimes people with hemophilia need injections of a clotting factor or factors to stop bleeding.

There are two main types of hemophilia. If you have hemophilia A, you have little to no clotting factor VIII (8). About 9 out of 10 people with hemophilia have type A. If you have hemophilia B, you’re missing or have low levels of clotting factor IX (9).

Hemophilia can be mild, moderate, or severe, depending on how much clotting factor is in the blood. About 7 out of 10 people who have hemophilia A have the severe form of the disorder. People who don’t have hemophilia have a factor VIII activity of 100 percent; people who have severe hemophilia A have a factor VIII activity of less than 1 percent.

In addition to being inherited, hemophilia also can be acquired, which means that you can develop it during your lifetime. It can develop if your body forms antibodies to the clotting factors in your bloodstream. The antibodies can block the clotting factors from working. Only inherited hemophilia is discussed in this article.

About 18,000 people in the United States have hemophilia. Each year, about
400 babies are born with the disorder. Hemophilia usually occurs only in males (with very rare exceptions).[/SIZE]
Causes Hemophilia?

If you have inherited hemophilia, you’re born with the condition. It’s caused by a defect in one of the genes that determine how the body makes blood clotting factors VIII or IX. These genes are located on the X chromosomes (KRO-muh-somz).

Chromosomes come in pairs. Females have two X chromosomes, while males have one X and one Y chromosome. Only the X chromosome carries the genes related to clotting factors.

A male who has the abnormal gene on his X chromosome will have hemophilia. A female must have the abnormal gene on both of her X chromosomes to have hemophilia; this is very rare.

A female is a “carrier” of hemophilia if she has the abnormal gene on one of her X chromosomes. Even though she doesn’t have the condition, she can pass the gene on to her children.

Below are two examples of how the hemophilia gene is inherited.

Inheritance Pattern for Hemophilia—Example 1
The diagram shows one example of how the hemophilia gene is inherited. In this example, the father doesn't have hemophillia (that is, he has two normal chromosomes—X and Y). The mother is a carrier of hemophilia (that is, she has one abnormal X chromosome and one normal X chromosome). Each daughter has a 50 percent chance of inheriting the abnormal gene from her mother and being a carrier. Each son has a 50 percent chance of inheriting the abnormal gene from his mother and having hemophilia.

Inheritance Pattern for Hemophilia—Example 2
http://www.nhlbi.nih.gov/health/dci/...ophilia_02.gif

The diagram shows one example of how the hemophilia gene is inherited. In this example, the father has hemophilia (that is, his X chromosome is abnormal). The mother isn’t a carrier of hemophilia (that is, she has two normal X chromosomes). Each daughter will inherit the abnormal gene from her father and be a carrier. None of the sons will inherit the abnormal gene from their father, and, therefore, none will have hemophilia.

Females who are carriers usually have enough clotting factors from their one normal X chromosome to prevent serious bleeding problems.

Very rarely, a girl is born with hemophilia. This can happen if her father has hemophilia and her mother is a carrier.

Some males with the disorder are born to mothers who aren’t carriers. In these cases, a mutation (random change) occurs in the gene as it is passed to the child.
Hemophilia Diagnosed?

If hemophilia is suspected or if you appear to have a bleeding problem, your doctor will take a personal and family medical history. This will reveal whether you or anyone in your family has a history of frequent and/or heavy bleeding and bruising. Your doctor also will do a physical exam and order blood tests.

Blood tests are used to determine:

How long it takes for your blood to clot
Whether your blood has low levels of any of the clotting factors
Whether one of the factors is completely missing from your blood
The test results will show if you have hemophilia, what type of hemophilia you have, and how severe it is.

Hemophilia A and B are classified as mild, moderate, or severe, depending on the amount of clotting factor VIII or IX in the blood.

Mild hemophilia 5–30 percent of normal factor
Moderate hemophilia 1–5 percent of normal factor
Severe hemophilia Less than 1 percent of normal factor

The degree of symptoms can overlap between the categories. For example, some people with mild hemophilia may have bleeding problems almost as often or as problematic as some people with moderate hemophilia.

Severe hemophilia can cause serious bleeding problems in babies. Therefore, children with severe hemophilia are usually diagnosed during the first year of life. People with milder forms of hemophilia may not be diagnosed until they're adults.

The bleeding problems of hemophilia A and hemophilia B are the same. Only special blood tests can tell which type a person has. Knowing which type is important because the treatments are different.

Pregnant women who are known carriers of hemophilia can have the condition diagnosed in their unborn child as early as 10 weeks into their pregnancy.

Women who are hemophilia carriers also can have “preimplantation diagnosis” to have a child without hemophilia. For this process, women have their eggs removed and then fertilized by sperm in a laboratory. The embryos that result from this fertilization are then tested for hemophilia. Only embryos that lack the condition will then be implanted in the womb.
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