What is Hemophilia?
Hemophilia is an inherited bleeding disorder, predominantly affecting males. There are two major forms of the disease: hemophilia A (factor VIII deficiency) and hemophilia B (factor IX deficiency). People with no family history can also develop hemophilia A. The National Hemophilia Foundation says this accounts for a third of all cases. It usually happens after a new or spontaneous gene mutation. There are about 20,000 people with hemophilia in the U.S.
Hemophilia may result from gene mutations: point mutations involving a single nucleotide, deletions of all or parts of the gene, and mutations affecting gene regulation. About 50% of cases of severe hemophilia A result from a major inversion of a section of the tip of the long arm of the X chromosome. Because factor VIII and factor IX genes are located on the X chromosome, hemophilia affects males almost exclusively. Daughters of hemophiliacs will be obligatory carriers, but sons will be normal. Each son of a carrier has a 50% chance of being a hemophiliac, and each daughter has a 50% chance of being a carrier. Rarely, random inactivation of one of the two X chromosomes in early embryonic life will result in a carrier's having a low enough factor VIII or IX level to experience abnormal bleeding.
Depending on the level of clotting factor in the blood, hemophilia may be mild, moderate, or severe. About 60% of people with hemophilia have severe hemophilia. Fifteen percent (15%) have the moderate type, and 25% have mild hemophilia. Those with severe hemophilia are at risk for bleeding after dental work, surgery, and trauma. They can also have internal bleeding with no trauma or injury. Repeated bleeding into joints and muscles can cause serious joint damage. In rare cases, a bleed in the head can cause death. Treatment of bleeding involves the prompt use of costly clotting factor products.