Merck Manual

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Michael B. Streiff

, MD, Johns Hopkins University School of Medicine

Reviewed/Revised Sep 2023
Topic Resources

Hemophilia is a hereditary bleeding disorder caused by a deficiency in one of two blood clotting factors: factor VIII or factor IX.

  • Several different gene abnormalities can cause the disorder.

  • People can bleed unexpectedly or after minor injuries.

  • Blood tests are needed for diagnosis.

  • Transfusions are given to replace missing clotting factors.

There are two primary forms of hemophilia.

  • Hemophilia A, which accounts for about 80% of all cases, is a deficiency in clotting factor VIII.

  • Hemophilia B is a deficiency in clotting factor IX.

The bleeding patterns and consequences of these two types of hemophilia are similar.

Did You Know...

  • Hemophilia can rarely affect females as well as males.

Symptoms of Hemophilia

The main symptom is excessive bleeding Bruising and Bleeding Bruising or bleeding after an injury is normal (see also How Blood Clots). However, some people have disorders that cause them to bruise or bleed too easily. Sometimes people bleed without any... read more Bruising and Bleeding . The bleeding may be into a joint or muscle, inside the abdomen or head, or from cuts, dental procedures, or surgery. A child who has hemophilia bruises easily.

The severity of the bleeding depends on how a particular gene abnormality affects the blood clotting activity of factor VIII or factor IX.

  • Mild hemophilia: Clotting activity is 5 to 49% of normal

  • Moderate hemophilia: Clotting activity 1 to 5% of normal

  • Severe hemophilia: Clotting activity less than 1% of normal

Mild hemophilia

People who have mild hemophilia may go undiagnosed. However, these people may bleed more than expected after surgery, dental extractions, or a severe injury.

Moderate hemophilia

People with moderate hemophilia have few unprovoked bleeding episodes, but surgery or injury may cause uncontrolled and fatal bleeding. In moderate hemophilia, the first bleeding episode usually occurs before a child is 18 months old. Bleeding may occur after a minor injury.

Severe hemophilia

When hemophilia is severe, serious episodes of bleeding occur and recur after minor injury or for no apparent reason.

In severe hemophilia, the first bleeding episode often occurs during or immediately after delivery. The infant may develop a collection of blood under the scalp (cephalhematoma) or may bleed excessively during circumcision.

Even an injection into a muscle can cause bleeding that results in a large bruise and collection of blood (hematoma). Recurring bleeding into the joints and muscles can lead to crippling deformities. Bleeding can swell the base of the tongue until it blocks the airway, making breathing difficult. A slight bump on the head can trigger substantial bleeding in the brain or between the brain and the skull, causing brain damage and death.

Diagnosis of Hemophilia

  • Blood tests

A doctor may suspect hemophilia in a child (especially a male) who bleeds without an apparent cause or bleeds more than expected after injury.

A blood test can determine whether the person's clotting is abnormally slow. If it is, further blood tests to measure the levels of factor VIII and factor IX can confirm the diagnosis of hemophilia and can determine its type and severity.

Treatment of Hemophilia

  • Replace the deficient clotting factor

People who have hemophilia should avoid situations that might provoke bleeding and should avoid drugs (for example, aspirin and probably also nonsteroidal anti-inflammatory drugs) that interfere with the function of platelets. They should be conscientious about dental care so that they will not need to have teeth extracted. If people who have milder forms of hemophilia need to have dental or other surgery, the drugs aminocaproic acid or desmopressin may be given to improve temporarily the body's ability to control bleeding so that transfusions can be avoided.

Often, treatment involves transfusions Plasma People are sometimes given transfusions of whole blood during severe bleeding (for example after an injury or pregnancy complications), but usually they are given only the blood component they... read more Plasma to replace the deficient clotting factor. These factors are normally present in the liquid component of blood (plasma). Clotting factors may be obtained from donated blood by concentrating or purifying them from plasma. Clotting factors purified from plasma are treated to inactivate most of the viruses that might be present in the donated plasma.

Clotting factors also may be produced in a laboratory using special technological procedures. These manufactured clotting factors are called highly purified recombinant factor concentrates. Recombinant forms of both factor VIII and factor IX are available. Because recombinant forms are not obtained from human donors, they do not have the slight risk of infection that is present with factors derived from donated blood.

The dose, frequency, and duration of therapy are determined by the site and severity of the bleeding problem. Clotting factors may also be used to prevent bleeding before surgery or at the first sign of bleeding.

Hemophilia A can be treated with emicizumab, a medication that binds to factors IX and X in a way that allows blood to clot without factor VIII.

A type of gene therapy has recently become available for hemophilia B. A similar medication is being tested for hemophilia A.

Some people with hemophilia develop antibodies to transfused clotting factors, which destroy the factors. As a result, factor replacement therapy becomes less effective. If antibodies are detected in the blood of a person with hemophilia, the dosage of the recombinant factor or plasma concentrates may be increased, or different types of clotting factors or medications to reduce the antibody levels may be needed.

Prevention of Hemophilia

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

Drugs Mentioned In This Article

Generic Name Select Brand Names
DDAVP, Minirin, Nocdurna, Noctiva, Stimate
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