Hemophilia is a medical condition in which the blood cannot clot properly, and it is caused by mutated genes. People who have hemophilia inherit the condition through genes and are born with the disease. These people carry mutated genes, which produce proteins, that cannot do an effective job in blood clotting. Three forms of hemophilia exist: hemophilia A, B and C. For each type of the disease, the specific causes of hemophilia are somewhat different.
People who have one of the forms of hemophilia suffer from excessive bleeding from wounds. Hemophilia A and B can even cause a person to bleed for no known reason internally, in the joints and the muscles of the body. All of the abnormal bleeding is caused by a problem with the blood. Blood carries substances called clotting factors, which react to an open wound by aggregating blood cells and closing up the wound, thereby stopping the bleeding. People who have hemophilia produce low levels of one of these clotting factor proteins.
The causes of hemophilia are always abnormal genes. In most cases, the abnormal genes come from the parents, but sometimes an egg with a normal parent gene can become mutated and cause disease. The causes of hemophilia A and B are mutated genes that are present on the X chromosome. Women have two X chromosomes and men have one X chromosome and one Y chromosome.
The presence of hemophilia A or B requires two copies of mutated genes, so far more men than women suffer from the disease. For a woman to have one of these forms of hemophilia, she must inherit two X chromosomes with the mutated gene, and this scenario occurs only when the father is hemophiliac and the mother carries the mutated gene. More often, the female child carries one mutated gene, but the other, healthy gene, prevents any disease.
In the case of hemophilia A, the clotting factor that is affected is Factor VIII, or Factor Eight. The people who have hemophilia A have mutated versions of the gene that produces Factor VIII. Factor IX, which is also known as Factor Nine, is the clotting protein that is not produced enough in people who have hemophilia B. Both of these mutated genes — the causes of hemophilia, in most cases — are located on the X chromosome.
Rarely, hemophilia C can occur. In this particular form of the disease, the affected person has low levels of Factor XI, or Factor Eleven. Both women and men can have this condition, because the gene for this clotting factor is not located on an X chromosome or a Y chromosome.
