Hemophilia

The Facts

Hemophilia is a rare bleeding disorder in which the blood does not clot normally. People with hemophilia have little or no blood clotting factors, which are needed for normal blood clotting.

There are 2 main types of hemophilia:

• Hemophilia A is also known as classic hemophilia because it is the most common. Clotting factor VIII (eight) is low or missing in hemophilia A.
• Hemophilia B may also be referred to as Christmas disease . Clotting factor IX (nine) is low or missing in hemophilia B.

Hemophilia is inherited – it is passed on from parents to children. In rare cases, a child may be born to a family that has no history of hemophilia. This may be due to an unknown family history of hemophilia or due to a random, new mutation (an abnormal change) in genes carrying hemophilia.

In Canada, hemophilia A affects fewer than 1 in 10,000 people. Hemophilia B is less common, affecting about 1 in 50,000 people. Hemophilia affects people of all races, colours, and ethnic backgrounds.

The most severe forms of hemophilia usually affect males only. Females may have severe hemophilia in certain instances, such as if the father has the disorder and the mother is a carrier. A carrier has the abnormal hemophilia genes but usually does not have the signs or symptoms of hemophilia. In some cases, women who are carriers may have symptoms of mild hemophilia.

Causes

Hemophilia is caused by mutations (abnormal changes) in the gene that makes clotting factors VIII or IX. These genes are located on the X chromosomes. Chromosomes are tiny structures found in every cell of our body; they hold our genes. Genes are the body's instructions for what we look like, how we act, and how our bodies work. Chromosomes come in pairs. Females have two X chromosomes and males have one X and one Y chromosome. Only the X chromosome holds the genes that make clotting factors VIII and IX.

A male who has an abnormal hemophilia gene on his X chromosome will have hemophilia. A female must have the abnormal gene on both of her X chromosomes to have hemophilia. If a female has the abnormal gene on only one of her X chromosomes, she is a hemophilia carrier. She does not usually have the signs and symptoms of hemophilia but may pass on the abnormal gene to her children.

Symptoms and Complications

The major signs and symptoms of hemophilia are excessive bleeding and easy bruising. A person with hemophilia does not bleed more quickly than other people, but he or she may bleed for a longer period of time before the body can form a clot. The extent of bleeding depends on how severe the hemophilia is.

Bleeding from external wounds is usually not serious. Examples of external bleeding are:

• bleeding in the mouth from a cut or a bite
• heavy bleeding from a minor cut
• nosebleeds for no obvious reason

Internal bleeding is much more serious. Examples of internal bleeding are:

• bleeding in the knees, elbows, or other joints, which may happen for no obvious reason. The joint may feel tight or painful and become swollen or warm to touch.
• blood in the urine or stool from bleeding in the kidneys, stomach, or intestine
• large bruises from bleeding into large muscles

A serious complication of hemophilia is bleeding in the brain, which can happen after a simple bump on the head or a more serious head injury, depending on how severe the hemophilia is. Signs and symptoms of bleeding in the brain are:

• bad headaches, neck pain, or stiffness, lasting a long time
• changes in behaviour
• changes in vision
• convulsions or seizures
• repeated vomiting
• sleepiness
• sudden weakness in the arms or legs

There are no differences in signs and symptoms between hemophilia A and B. Only special blood tests can tell which type of hemophilia you have. Knowing which type you have is important, as the treatment choices are different.

Making the Diagnosis

People with severe hemophilia can have serious bleeding problems early in life and are often diagnosed during the first year of life. Those with mild hemophilia might not be diagnosed until later in life.

Hemophilia is usually diagnosed by blood tests, family history, and any unusual signs of bleeding as described above. Blood tests are used to find out:

• how long it takes for your blood to clot
• the levels of clotting factors in your blood
• whether any clotting factors are partially or completely missing in your blood

The test results will help confirm whether or not you have hemophilia, which type of hemophilia you have, and how severe it is. It is classified as mild , moderate , or severe depending on how much clotting factor VIII or IX is in your blood.

If a pregnant woman is known to be a carrier, doctors can perform tests before her baby's birth to diagnose hemophilia. Testing is done by chorionic villus sampling (CVS) or amniocentesis. CVS is performed as early as Week 11, while amniocentesis is performed after Week 16. Other tests include blood sampling from the baby or the mother, as well as ultrasound testing.

Treatment and Prevention

The type of treatment depends on the type of hemophilia you have, how severe the hemophilia is, your daily activities, and any dental or medical procedures you may be having.

The main treatment for hemophilia is clotting factor replacement therapy. Clotting factor VIII or IX is infused into a vein. These clotting factors can be made from human blood that is screened and treated to prevent viral infections. With current technology, the risk of getting an infectious disease from human clotting factors is very small. Clotting factors can also be made in a lab instead of human blood; these are called recombinant clotting factors.

Replacement therapy may be given as prophylaxis , which means giving it on a regular basis to prevent bleeding, or on demand, only when an episode of bleeding occurs.

Problems that can come with factor replacement therapy include:

• damage to joints, muscles, or other parts of the body because of a delay in treatment
• developing antibodies that attack the clotting factor
• developing viral infections from clotting factors made from human blood

Very rarely, the body may form antibodies that attack the clotting factor replacement and prevent treatment from working. These antibodies are also called inhibitors. In hemophilia A, antibodies may develop in about a third of people with the condition. In hemophilia B, antibodies may develop in about 1% of people. They are more common in people with severe hemophilia. In these cases, other types of treatments might be used instead.

Other treatments for hemophilia include:

• desmopressin (DDAVP): Desmopressin is a man-made hormone used to treat mild bleeds in those with hemophilia A. It causes the body to release more factor VIII and von Willebrand factor. Von Willebrand factor helps keep factor VIII in the bloodstream longer. It can be given as an injection or as a nasal spray. It is given only in certain situations, because its effects may wear off if it is given too often.
• tranexamic acid: Tranexamic acid belongs to a class of medications called antifibrinolytics which stop blood clots from breaking down. It may be used with factor replacement therapy as a pill or infused into a vein. It is usually used before dental work or to treat bleeding from the mouth.
• gene therapy: Researchers are trying to find ways to correct the abnormal genes that cause hemophilia. Gene therapy is not commonly used yet, as more research is needed.
• emicizumab: emicizumab is a medication used to treat hemophilia A. It allows blood to clot without factor VIII by binding to factors IX and X.

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