The A to B of hemophilia and hemophilia treatment

The basics

Hemophilia is a type of bleeding disorder that causes the blood to take a long time to clot. This can cause abnormal bleeding, or bleeding that won't stop. People with hemophilia have too little—or even none—of a protein in the blood called clotting factor. Hemophilia most often affects males and, in most cases, is inherited (passed down through families). Originally, hemophilia was thought to be a single disease. In the 1950s, health care providers discovered that there are actually two forms of the disease: hemophilia A and hemophilia B. Because of this, each disease is treated with its own specific factor replacement medication.

Classifying hemophilia

Hemophilia is classified as mild, moderate, or severe, depending on the level of clotting factor in the blood. While more severe hemophilia is usually diagnosed during infancy, non-severe hemophilia may not be diagnosed until adulthood. People without hemophilia normally have a range of factor VIII or IX that varies from 50% to 150%.

Hemophilia severity Factor VIII/IX level
Mild More than 5% normal
Moderate 1% to 5% of normal
Severe Less than 1% of normal
How hemophilia is inherited

Hemophilia is an X-linked genetic disorder. The infographic below helps explain how inherited genes play a role.

Female without factor VIII/IX deficiency gene

Female carrier of factor VIII/IX deficiency gene

Male without Hemophilia

Male with Hemophilia

Hemophilia signs and symptoms

The signs and symptoms of hemophilia can include:

  • Bleeding following injury or surgery
  • Spontaneous bleeding (spontaneous means that the bleeding occurs without an apparent cause)
  • Bruising
  • Pain and swelling resulting from bleeding into joints and muscles
  • Blood in the urine or stool
  • Heavy bleeding following circumcision
  • Unexplained nosebleeds
  • Brain bleeds