What is hemophilia?
Hemophilia is an inherited bleeding, or coagulation, disorder. Children with hemophilia lack the ability to stop bleeding because of the low levels, or complete absence, of specific proteins, called "factors," in their blood that are necessary for clotting. Proper clotting of blood helps prevent excessive bleeding.
What are the different types of hemophilia?
There are many factors in the blood that are involved in the forming of clots to stop bleeding. A child with hemophilia is missing, or has a low supply of, one of the factors needed in order for the blood to clot. Two common factors that affect blood clotting are factor VIII and factor IX.
Hemophilia is classified by its level of severity. Hemophilia may be mild, moderate, or severe, depending on the level of the blood clotting factors in the blood.
The three main forms of hemophilia include the following:
Hemophilia A--caused by a lack of the blood clotting factor VIII; approximately 85 percent of hemophiliacs have type A disease.
Hemophilia B--caused by a deficiency of factor IX.
Hemophilia C--some doctors use this term to refer to a lack of clotting factor XI
von Willebrand disease--a part of the factor VIII molecule known as von Willebrand factor or ristocetin cofactor is reduced. The von Willebrand factor involves helping the platelets (blood cells that control bleeding) attach to the lining of a vein or artery. This missing factor results in prolonged bleeding time because the platelets are unable to attach to the wall of the vessel and form a plug to stop the bleeding. This disease is similar to hemophilia, but is not usually called by this name. It is more common and usually milder than hemophilia.
What causes hemophilia?
Hemophilia types A and B are inherited diseases passed on to children from a gene located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. A female carrier of hemophilia has the hemophilia gene on one of her X chromosomes. When a hemophilia carrier female is pregnant, there is a 50/50 chance that the hemophilia gene will be passed on. If the gene is passed on to a son, he will have the disease. If the gene is passed on to a daughter, she will be a carrier. If the father has hemophilia but the mother does not carry the hemophilia gene, then none of the sons will have hemophilia disease, but all of the daughters will be carriers.
In about one-third of the children with hemophilia, there is no family history of the disorder. It is believed that, in these cases, the disorder could be related to a new gene mutation. Tests are available to possible carriers to help determine whether or not they, in fact, carry the abnormal gene.
Carriers of the hemophilia gene usually have normal levels of clotting factors but may bruise easily, may bleed more with surgeries and dental work, and/or have frequent nosebleeds or excessive menstrual bleeding.
Hemophilia C usually does not cause problems, but some patients may have bleeding after surgery.
With von Willebrand disease, the missing protein, von Willebrand factor (vWF), is not on the X chromosome, but on a chromosome that is not gender determined; so, the disease can affect both males and females equally. Its inheritance is autosomal dominant, which means that a parent with the gene has a 50/50 chance to pass it on.
Children with von Willebrand disease may have inherited the disorder or it is possible to have had the disease caused by certain medications, autoimmune disorders, kidney problems, and certain forms of cancer.
What are the symptoms of hemophilia?
Because hemophilia is a bleeding disorder, the most common symptom of the disorder is excessive, uncontrollable bleeding. Hemophiliacs do not bleed faster than normal children; they bleed for a longer time.
The severity of hemophilia is determined by the amount of clotting factors in the blood. Those affected with hemophilia that have levels greater than 5 percent (100 percent being average for unaffected children) usually experience bleeding only with major surgeries or tooth extractions. These children may not even be diagnosed until bleeding complications from a surgery occur.