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.