What is hemophilia?

Hemophilia is a rare hereditary (inherited) bleeding disorder in which blood cannot clot normally at the site of a wound or injury. The disorder occurs because certain blood clotting factors are missing or do not work properly. This can cause extended bleeding from a cut or wound. Spontaneous internal bleeding can occur as well, especially in the joints and muscles. Hemophilia affects males much more often than females.

There are two types of inherited hemophilia:

  • Type A, the most common type, is caused by a deficiency of factor VIII, one of the proteins that helps blood to form clots.
  • Type B hemophilia is caused by a deficiency of factor IX.

Although hemophilia is usually diagnosed at birth, the disorder can also be acquired later in life if the body begins to produce antibodies that attack and destroy clotting factors. However, this acquired type of hemophilia is very rare.

What causes hemophilia?

The genes that regulate production of factors VIII and IX are found on the X chromosome only. Hemophilia is caused by an abnormal gene on the X chromosome. If a woman carries the abnormal gene on one of her chromosomes (females have a pair of X chromosomes), she will not have hemophilia herself, but she will be a carrier of the disorder. That means that she can pass the gene for hemophilia on to her children. There is a 50% chance that any of her sons will inherit the gene and will be born with hemophilia. There is also a 50% chance that any of her daughters will be carriers of the gene, without having hemophilia themselves.

It is very rare for a girl to be born with hemophilia, but it can happen if the father has hemophilia and the mother carries the gene for hemophilia. Their daughter will then have the abnormal gene on both of her X chromosomes.

In about 20% of all cases of hemophilia, the disorder is caused by a spontaneous gene mutation.

How common is hemophilia?

Hemophilia is an extremely rare disorder. Hemophilia A affects 1 in 5,000 to 10,000 males. Hemophilia B is less common, affecting 1 in 25,000 to 30,000 males. Around 60 to 70% of people with hemophilia A have the severe form of the disorder, about 15% have the moderate form, and the rest have mild hemophilia. Hemophilia can occur in all races and ethnic groups.

What are the symptoms of hemophilia?

Prolonged external bleeding, and bruising that occurs easily or for no apparent reason, are two major symptoms of hemophilia.

The symptoms of hemophilia vary depending on whether the person has the mild, moderate, or severe form of the disorder. For people with severe hemophilia, bleeding episodes occur more often and with little or no provocation. For those with moderate hemophilia, prolonged bleeding tends to occur after a more significant injury. People with the mild form of hemophilia might have unusual bleeding only after a major injury, surgery, or trauma.

People with hemophilia may have any type of internal bleeding (inside the body), but most often in the muscles and joints, such as the elbows, knees, hips, shoulders, and ankles. Often there is no pain at first, but if it continues, the joint may become hot to the touch, swollen, and painful to move. Recurrent bleeding into the joints and muscles can cause permanent damage, such as joint deformity and reduced mobility (ability to get around).

Bleeding in the brain is a very serious problem for those with severe hemophilia, and may be life-threatening. Signs of bleeding in the brain may include changes in behavior, excessive sleepiness, persistent headaches and neck pain, double vision, vomiting, and convulsions or seizures.

How is hemophilia diagnosed?

A doctor will perform a physical examination to rule out other conditions. If you have symptoms of hemophilia, the doctor will obtain information about your family’s medical history, since this disorder tends to run in families.

Blood tests are then performed to determine how much factor VIII or factor IX is present in your blood. These tests will show which type of hemophilia you have, and whether it is mild, moderate, or severe, depending on the level of clotting factors in the blood:

  • People who have 5-30% of the normal amount of clotting factors in their blood have mild hemophilia.
  • People with 1-5% of the normal level of clotting factors have moderate hemophilia.
  • People with less than 1% of the normal clotting factors have severe hemophilia

How is hemophilia treated?

The treatment will depend on the type and severity of the disorder. It consists of replacement therapy, in which concentrates or recombinant forms of the clotting factors VIII or IX are given as needed to replace the blood clotting factors that are missing or deficient. These blood factor concentrates are made from donated human blood that has been treated and screened to reduce the risk of transmitting infectious diseases, such as hepatitis and HIV. Recombinant clotting factors, which are made in the laboratory and not from human blood, are also in common use today.

During replacement therapy, the clotting factors are injected or infused (dripped) into a patient’s vein. Usually, people with mild hemophilia do not require replacement therapy unless they are going to have surgery. In cases of severe hemophilia, treatment may be given as needed to stop bleeding when it occurs. Patients who have very frequent bleeding episodes may be candidates for prophylactic factor infusions; that is, infusions given two or three times per week to prevent bleeding from occurring.

Some people with the mild or moderate form of hemophilia type A can be treated with desmopressin (DDAVP), a synthetic (man-made) hormone that helps to stimulate the release of factor VIII and another blood factor that carries and binds to it. Sometimes DDAVP is given as a preventive measure before a person with hemophilia has dental work or participates in sports. DDAVP is not effective for people with type B hemophilia or severe hemophilia type A.


  • National Heart, Lung, and Blood Institute. What is hemophilia? Accessed 10/29/2013.
  • Centers for Disease Control and Prevention. Hemophilia Accessed 10/29/2013.

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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 6/18/2013...#14083