Hemophilia | Symptoms & Causes

What are the symptoms of hemophilia?

The symptoms and signs of hemophilia A and B are similar and may include:

  • large bruises, known as a hematoma, caused by bleeding under the skin
  • spontaneous or injury related bleeding into the muscles or joints, causing swelling and tightness
  • bleeding of the mouth and gums following tooth extractions or surgery
  • bleeding following vaccinations or shots
  • blood in the urine or stool
  • frequent and difficult-to-stop nosebleeds

What causes hemophilia?

A mutation or change in the gene that regulates the production of factor VIII or IX causes hemophilia. These particular genes related to clotting factors are located on the X chromosome. Females have two X chromosomes (XX), and males have one X and one Y (XY). A father will pass a hemophilia gene only to daughters; however, mothers can pass a hemophilia gene to sons or daughters. 

A male who has an abnormal copy of this gene on his x chromosome will not be able to make clotting factor. This is hemophilia. Because females have two x chromosomes, they almost always have at least one working copy of the gene. This is why they are much less likely to have hemophilia. 

A female who has the “hemophilia gene” on just one of her X chromosomes is less likely to have hemophilia, because her other X chromosome typically will have a normal copy of the factor gene and allow for normal factor production. While females with the hemophilia gene, called “hemophilia carriers,” have the potential to pass the hemophilia gene to their offspring, it is important to understand that some female carriers may also have low factor VIII or IX levels and have mild hemophilia and abnormal bleeding symptoms. In some rare cases, females can also have more severe forms of hemophilia. 

Although hemophilia is primarily an inherited condition, about one third of cases rise from a new mutation, so there will not be any family history of hemophilia or related bleeding symptoms.