Hemophilia A is most typically a genetic bleeding disorder caused by a missing or defective clotting protein called factor VIII. It’s also called classical hemophilia or factor VIII deficiency. In rare cases, it isn’t inherited, but instead caused by an abnormal immune reaction within your body.
People with hemophilia A bleed and bruise easily, and their blood takes a long time to form clots. Hemophilia A is a rare, serious condition that has no cure, but is treatable.
Read on to get a better understanding of this bleeding disorder, including causes, risk factors, symptoms, and potential complications.
Hemophilia A is most often a genetic disorder. This means that it’s caused by changes (mutations) to a particular gene. When this mutation is inherited, it’s passed down from parents to children.
The specific gene mutation that causes hemophilia A leads to a deficiency in a clotting factor called factor VIII. Your body uses a variety of clotting factors to help form clots at a wound or injury.
A clot is a gel-like substance made out of elements in your body called platelets and fibrin. Clots help stop the bleeding from an injury or cut and allow it to heal. Without enough factor VIII, bleeding will be prolonged.
Less often, hemophilia A occurs randomly in a person with no prior family history of the disorder. This is known as acquired hemophilia A. It’s typically caused by a person’s immune system incorrectly making antibodies that attack factor VIII. Acquired hemophilia is more common in people between the ages of 60 and 80 years old and in pregnant women. Acquired hemophilia has been known to resolve, unlike the inherited form.
There are three types of hemophilia: A, B (also known as Christmas disease), and C.
Hemophilia A and B have very similar symptoms, but are caused by different gene mutations. Hemophilia A is caused by a deficiency in clotting factor VIII. Hemophilia B results from a deficiency in factor IX.
On the other hand, hemophilia C is due to a factor XI deficiency. Most people with this type of hemophilia have no symptoms and often no bleeding into joints and muscles. Prolonged bleeding usually only occurs after an injury or surgery. Unlike hemophilia A and B, hemophilia C is most common in Ashkenazi Jews and affects both men and women equally.
Factor VIII and IX aren’t the only clotting factors your body needs to form clots. Other rare bleeding disorders can occur when there are deficiencies of factors I, II, V, VII, X, XII, or XIII. However, deficiencies in these other clotting factors are extremely rare, so not much is known about these disorders.
All three types of hemophilia are considered rare diseases, but hemophilia A is the most common of the three.
Hemophilia is rare — it occurs in only 1 out of every 5,000 births. Hemophilia A occurs equally in all racial and ethnic groups.
It’s called an X-linked condition because the mutation that causes hemophilia A is found on the X chromosome. Males determine the sex chromosomes of a child, giving an X chromosome to daughters and a Y chromosome to sons. So females are XX and males are XY.
When a father has hemophilia A, it’s located on his X chromosome. Assuming the mother isn’t a carrier of or has the disorder, none of his sons will inherit the condition, because all of his sons will have a Y chromosome from him. However, all of his daughters will be carriers because they received one hemophilia-affected X chromosome from him and an unaffected X chromosome from the mother.
Women who are carriers have a 50 percent chance of passing the mutation on to their children, because one X chromosome is affected and the other isn’t. If her sons inherit the affected X chromosome, they will have the disease, as their only X chromosome is from their mother. Any daughters who inherit the affected gene from their mother will be carriers.
The only way a woman can develop hemophilia is if the father has hemophilia and the mother is a carrier or has the disease as well. A woman requires the hemophilia mutation on both X chromosomes to show signs of the condition.
People with hemophilia A bleed more often and for a longer time than people without the disease. The bleeding may be internal, such as within joints or muscles, or external and visible, as from cuts. The severity of the bleeds depends on how much factor VIII a person has in their blood plasma. There are three levels of severity:
Approximately 60 percent of people with hemophilia A have severe symptoms. Symptoms of severe hemophilia include:
- bleeding following an injury
- spontaneous bleeding
- tight, swollen, or painful joints caused by bleeding in the joints
- heavy bleeding from a minor cut
- blood in the urine
- blood in the stool
- large bruises
- bleeding gums
Roughly 15 percent of people with hemophilia A have a moderate case. The symptoms of moderate hemophilia A are similar to severe hemophilia A, but are less serious and occur less often. Symptoms include:
- prolonged bleeding after injuries
- spontaneous bleeding without obvious cause
- bruising easily
- joint stiffness or pain
About 25 percent of hemophilia A cases are considered mild. Often a diagnosis isn’t made until after a serious injury or a surgery. Symptoms include:
- prolonged bleeding after a serious injury, trauma, or surgery, such as a tooth extraction
- easy bruising and bleeding
- unusual bleeding
A doctor makes a diagnosis by measuring the level of factor VIII activity in a sample of your blood.
If there is a family history of hemophilia, or a mother is a known carrier, diagnostic tests can be done during pregnancy. This is called prenatal diagnosis.
Repetitive and excessive bleeding can lead to complications, especially if it goes untreated. These include:
- severe anemia
- joint damage
- deep internal bleeding
- neurological symptoms from bleeding within the brain
- an immune reaction to clotting factor treatment
Receiving infusions of donated blood also increases your risk of infections, such as hepatitis. However, nowadays donated blood is tested thoroughly prior to transfusion.
There is no cure for hemophilia A and those with the disorder require life-long treatment. It’s recommended that individuals receive treatment at a specialized hemophilia treatment center (HTC) whenever possible. In addition to treatment, HTCs provide resources and support.
Treatment involves replacing the missing clotting factor via transfusions. Factor VIII can be obtained from blood donations, but is now usually created artificially in a lab. This is called recombinant factor VIII.
The frequency of treatment depends on the severity of the disorder:
Mild hemophilia A
Those with mild forms of hemophilia A may only need replacement therapy after a bleeding episode. This is referred to as episodic or on-demand treatment. Infusions of a hormone known as desmopressin (DDAVP) can help stimulate the body to release more clotting factor to stop a bleeding episode. Medications known as fibrin sealants may also be applied to a wound site to help promote healing.
Severe hemophilia A
People with severe hemophilia A may receive periodic infusions of factor VIII to help prevent bleeding episodes and complications. This is called prophylactic therapy. These patients can also be trained to give infusions at home. Severe cases may need physical therapy to ease pain caused by bleeding in the joints. In severe cases, surgery is needed.