Pediatric Hemophilia Symptoms & Causes

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Contact the Boston Hemophilia Center

What causes hemophilia? 

Normal blood contains a number of different proteins called “factors” that help form clots and stop bleeding. If one of these factors is lacking or defective, the blood cannot clot properly, potentially resulting in a bleeding disorder.

The two main types of hemophilia are hemophilia A and hemophilia B.

Hemophilia A is caused by an abnormally low level of factor VIII.

Hemophilia B is caused by an abnormally low level of factor IX.

  • Normal plasma levels of factor VIII and IX range from 50% to 150%.
  • Hemophilia can be mild, moderate or severe, depending on the factor level.
  • People with severe hemophilia have <1% of factor in their blood.

Hemophilia A and B are inherited disorders passed from mother to child through the X-chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). A male who carries the hemophilia gene on his X chromosome has hemophilia. A female who carries the hemophilia gene on one of her X chromosomes is a “carrier.” A person can have either hemophilia A or B, but not both.

About one-third of children with hemophilia have no family history of the disease and their hemophilia is due to a new genetic mutation.


What are the symptoms of hemophilia?

The most common symptoms of hemophilia in children are excessive bleeding and easy bruising. Children with hemophilia don’t bleed faster than normal, they bleed for a longer time because their blood clots slowly. The extent of bleeding depends on the severity of hemophilia. Children with mild hemophilia may have no bleeding episodes unless they have excessive bleeding from trauma or a dental procedure or surgery. Children with severe hemophilia get spontaneous joint bleeds.

Symptoms of hemophilia in children may include:

  • Bruises from small accidents, which may result in large hematomas (collection of blood under the skin that cause swelling)
  • Nosebleeds
  • Bleeding in the mouth or gums from minor trauma or while brushing teeth
  • Blood in the urine or stool
  • Muscle bleeds causing pain and swelling
  • Joint bleeds causing pain, swelling and immobility
  • Internal bleeding such as head bleed, which can be life-threatening

When to see a doctor

You should call your doctor immediately if you notice any of the above symptoms.

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