A bleeding disorder caused by a deficiency in blood clotting factors. Hemophilia A (often called classic hemophilia) is a hereditary disorder in which the clotting ability of the blood is impaired, which can lead to excessive bleeding. This type accounts for about 80 percent of all hemophilia cases. Although minor injuries and punctures are usually not a problem, uncontrolled internal bleeding can cause pain, swelling, and permanent damage to joints and muscles.
Hemophilia A occurs in about one out of 10,000 live male births. About 17,000 Americans have hemophilia, most of whom are men. Very rarely does it occur in girls and women. The only way a woman could ever have hemophilia is if her father has the disease and her mother carries the gene. With proper treatment, most boys with hemophilia will grow up to lead relatively normal lives.
Severity of symptoms can vary. Prolonged bleeding is the hallmark of hemophilia A, often first appearing when an infant is circumcised. Additional bleeding incidences appear as the baby begins to move around. Mild cases may go unnoticed until later in life, when the child experiences excessive bleeding and clotting problems after surgery or accidents. Internal bleeding may happen anywhere, and bleeding into joints is common.
The severity of the symptoms of hemophilia A depends on how a particular gene abnormality affects the activity of clotting factor VIII. When the activity is less than 1 percent of normal, episodes of severe bleeding recur for no apparent reason. Symptoms may include bruising, spontaneous bleeding, bleeding into joints, and associated pain and swelling, gastrointestinal tract and urinary tract hemorrhage, blood in the urine or stool, and prolonged bleeding from cuts, tooth extraction, and surgery.
Children whose clotting activity is 5 percent of normal may have only mild hemophilia with only rare unprovoked bleeding episodes. However, surgery or injury may cause uncontrolled bleeding, which can be fatal. Milder hemophilia may not be diagnosed at all, although some people whose clotting activity is 10 percent to 25 percent of normal may still have prolonged bleeding after surgery, dental extractions, or a major injury.
Typically, the first bleeding episode occurs after a minor injury before 18 months of age. A child who has hemophilia bruises easily, so that even an injection into a muscle can cause a large bruise. Recurring bleeding into the joints and muscles can ultimately lead to crippling deformities. Bleeding can swell the base of the tongue until it blocks the airway, making breathing difficult, or a bump on the head can trigger substantial bleeding in the skull, causing brain damage and death.
Hemophilia A is caused by an inherited sex-linked recessive trait with a defective gene on the X chromosome. Females are carriers of this trait. Half of the male offspring of female carriers have the disease and half of their female offspring are carriers. All female children of a male with hemophilia are carriers of the trait.
However, a third of all children with hemophilia A do not have a family history of the disorder. In these cases, hemophilia develops as the result of a new or spontaneous gene mutation.
Genetic counseling may be advised for carriers, who can be identified by genetic testing. A girl or woman is definitely a hemophilia carrier if she is:
- the biological daughter of a man with hemophilia
- the biological mother of more than one son with hemophilia
- the biological mother of one hemophilic son who has at least one other blood relative with hemophilia
A woman may or may not be a hemophilia carrier if she is:
- the biological mother of one son with hemophilia
- the sister of a male with hemophilia
- an aunt, cousin, or niece of an affected male related through maternal ties
- the biological grandmother of one grandson with hemophilia
A laboratory analysis of blood samples can determine whether the child’s clotting is abnormally slow. If it is, the doctor can confirm the diagnosis of hemophilia A and can determine the severity by testing the activity of factor VIII.
Hemophilia is treated by giving the child the missing clotting factor. How much clotting factor is given depends upon where and how much the child is bleeding and the size of the patient. In the past, mild hemophilia A was typically treated with an infusion of a substance that triggered the release of factor VIII stored within the lining of blood vessels.
Clotting factors are found in plasma and in plasma concentrates. Some plasma concentrates can be used at home, either on a regular basis to prevent bleeding or when bleeding first starts. Both the dose and frequency depend on the severity of the bleeding problem, and the dose is adjusted according to the results of periodic blood tests. During a bleeding episode, more clotting factors are needed.
To prevent a bleeding crisis, children with hemophilia and their families can be taught to administer clotting factor concentrates at home at the first signs of bleeding. People with severe forms of the disease may need regular preventive infusions.
Depending on the severity of the disease, clotting factors may be given before dental extractions and surgery to prevent bleeding. Immunization with hepatitis B vaccine is necessary because of the increased risk of exposure to hepatitis due to frequent infusions of blood products.
Children with hemophilia should avoid situations that might cause bleeding and take good care of their teeth so they will not need to have teeth pulled. Children with hemophilia also should avoid drugs that worsen bleeding problems, including aspirin, heparin, warfarin, and painkillers such as nonsteroidal anti-inflammatory drugs.
Complications of hemophilia include chronic joint deformities caused by bleeding into the joint or brain hemorrhage. Some children with hemophilia develop antibodies to transfused clotting factors so that the transfusions become ineffective. If antibodies are detected in blood samples, the dosage of the plasma concentrates may be increased, or different types of clotting factors or drugs to reduce the antibody levels may be used.
In the past, plasma concentrates carried the risk of transmitting blood-borne diseases such as hepatitis and AIDS. About 60 percent of people with hemophilia treated with plasma concentrates in the early 1980s were infected with HIV. Today, however, the risk of transmitting HIV infection through plasma concentrates has been virtually eliminated by using screened and processed blood and a genetically engineered clotting factor VIII (Recombinant).
Researchers are studying ways to use gene therapy to treat hemophilia by using a genetically engineered virus to deliver beneficial genes. Gene therapy is a novel form of disease treatment in which the active agent is a sequence of DNA, instead of the proteins or small molecules now used as drugs.