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The Manual's Editorial Staff

Reviewed/Revised Mar 2022 | Modified Sep 2022
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What is hemophilia?

  • Hemophilia makes you bleed a lot from small injuries or even without an injury

  • Almost everyone with hemophilia is male

  • Boys inherit hemophilia from their mother

  • People with hemophilia can't make enough of a clotting factor (proteins that help blood to clot)

  • Doctors diagnose hemophilia with a blood test

  • You may need injections of a clotting factor in your veins (IV)

What causes hemophilia?

Clotting factors are proteins in your blood that help make blood clots. Blood clots plug up bleeding blood vessels. There are over a dozen different clotting factors.

  • In hemophilia, you inherit an abnormal gene so you don't make enough of one of the clotting factors

  • There are 2 types of hemophilia, A and B, depending on which clotting factor is decreased

Hemophilia isn't equally severe in everyone who has it. Some people make very little of the affected clotting factor. Other people make some of the clotting factor but not quite enough. The less clotting factor you have the more severe your tendency to bleed.

What are the symptoms of hemophilia?

The main symptom of hemophilia is:

You may bleed from the outside, like from a cut or from your nose. Or you may bleed on the inside. For example, if you twist your knee or bang your leg, it may swell up with blood.

Because people who have hemophilia are born with it, blood clotting problems usually show up in young children unless the problem is very mild.

How much you bleed depends on how severe your hemophilia is.

If you have mild hemophilia, you may:

  • Bleed more than usual, but only after surgery, dental work, or an injury

  • Never be diagnosed

If you have moderate hemophilia, you may:

  • Sometimes bleed without any apparent injury

  • During surgery or after an injury, have heavy bleeding that's hard to control and can cause death

If you have severe hemophilia, you may:

  • Often have serious bleeding after a minor injury or for no clear reason

  • Have your tongue swell up from bleeding inside the tongue muscle, which can cut off your air

  • Have major bleeding in your brain from a slight bump to the head, causing brain damage or death

Bleeding inside the same joint can cause crippling joint damage.

How can doctors tell if I have hemophilia?

Doctors suspect hemophilia in a child (especially a boy) who bleeds a lot and bruises easily, especially if the child has family members with hemophilia.

To diagnose hemophilia, doctors do blood tests to see if your blood clots at a normal rate and whether there are enough clotting factors.

Genetic testing can show if a woman is a carrier of the abnormal genes that cause hemophilia. Pregnant women with these genes can have their baby tested during pregnancy.

How do doctors treat hemophilia?

If you have hemophilia, doctors may:

  • Do transfusions of clotting factor to help your blood to clot

  • Have you take medicine to lessen bleeding

Doctors will also tell you to:

  • Avoid situations that might cause you to be injured and bleed

  • Avoid medicines, such as aspirin, that can make bleeding worse

  • Take good care of your teeth and mouth so you won't need to have teeth pulled

Where can I get more information about hemophilia?

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