This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Hemophilia A is an inherited bleeding disorder in which the blood does not clot normally. People with hemophilia A will bleed more than normal after an injury, surgery, or dental procedure. This disorder can be severe, moderate, or mild. In severe cases, heavy bleeding occurs after minor injury or even when there is no injury (spontaneous bleeding). Bleeding into the joints, muscles, brain, or organs can cause pain and other serious complications. In milder forms, there is no spontaneous bleeding, and the disorder might only be diagnosed after a surgery or serious injury. Hemophilia A is caused by having low levels of a protein called factor VIII. Factor VIII is needed to form blood clots. The disorder is inherited in an X-linked recessive manner and is caused by changes (mutations) in the F8 gene. The diagnosis of hemophilia A is made through clinical symptoms and specific laboratory tests to measure the amount of clotting factors in the blood. The main treatment is replacement therapy, during which clotting factor VIII is dripped or injected slowly into a vein. Hemophilia A mainly affects males. With treatment, most people with this disorder do well. Some people with severe hemophilia A may have a shortened lifespan due to the presence of other health conditions and rare complications of the disorder.
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