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Hemoplilia 101

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 do not have enough clotting factor VIII or IX in their blood; sometimes, they do not have any. Depending on the level of clotting factor a person does have in their blood, hemophilia is classified as mild, moderate, or severe.

Hemophilia Severity




Factor VIII/IX Level

More than 5% of normal

1% to 5% of normal

Less than 1% of normal

The genes associated with hemophilia are located on the X chromosome. This means that:

  • A man with hemophilia cannot pass on the condition to his son
  • A woman who carries the altered gene on her X chromosome has a 50% chance of passing on hemophilia to her son and a 50% chance of passing down carrier status and, depending on the level of FVIII or FIX, potentially hemophilia to her daughter
  • Hemophilia occurs mainly in men, but women may also have hemophilia if their carrier status substantially lowers their levels of clotting factor or if both X chromosomes contain a copy of the altered gene

Hemophilia Village DNA

Common signs and symptoms of hemophilia

  • Bleeding following injury or surgery
  • Spontaneous bleeding (spontaneous means that the bleeding occurs without an apparent cause)
  • Easy bruising in early childhood
  • Pain and swelling resulting from bleeding into joints and muscles
  • Blood in the urine or stool
  • Heavy bleeding following circumcision
  • Heavy menstrual periods
  • Bleeding in the brain


Hemophilia A (factor VIII deficiency)

  • The most common form of hemophilia ≈1 in 5000 male births (or 1 in 10,000 people)
  • Also called "classic" hemophilia

Information about a prescription option for hemophilia A


Hemophilia B (factor IX deficiency)

  • The second most common form of hemophilia occurs in ≈1 in 25,000 male births (or 1 in 50,000 people)
  • Sometimes called Christmas disease after Stephen Christmas, the first patient described with this disease

Information about a prescription option for hemophilia B