Hemophilia B, also called factor IX deficiency, is a blood clotting disorder caused by a deficiency of a clotting protein called factor IX. Blood clots are clumps of different types of blood cells and clotting factors that stop bleeding after an injury to allow wound healing. People with hemophilia, including factor IX deficiency, do not form clots properly. This leads to bleeding that can range from mild to severe. Hemophilia B is the second most common type of hemophilia. Hemophilia B is sometimes called Christmas disease after Stephen Christmas, who was the first patient described with this disease. The first report of this deficiency was published during the Christmas season of 1952.
The process of blood clotting is called coagulation, or hemostasis. When a blood vessel (vein or artery) becomes injured, it narrows to slow blood flow so that clotting can begin. At the same time, the blood that has leaked outside of the injured blood vessel presses against the vessel to help prevent further blood loss. Blood cells called platelets are activated to move toward the site of injury. Once platelets reach the site of injury, a series of reactions facilitated by enzymes called "coagulation factors" lead to the activation of a protein called thrombin. This protein converts a blood clotting factor called fibrinogen into long strands that form a net around the platelets and blood cells. This net helps trap more platelets to form a blood clot. The blood clot, also called a thrombus, is a temporary plug to control bleeding in order to allow wound healing.
Once the platelets are clumped together, they change in shape from round to spiny so that they stick to the wall of the broken blood vessel. Internal blood clots appear as bruises under the skin while others are visible on the surface of the skin as scabs. Once the blood vessel is healed, other blood factors are released to destroy the clot and dissolve it into the blood.
Symptoms of hemophilia B usually appear during infancy or early childhood. Due to an inability to properly form clots, patients experience prolonged bleeding in response to injuries, such as scrapes, bruises, cuts, or nosebleeds, as well as after surgical procedures. Some patients may experience pain and swelling in their joints, including the knees, elbows, ankles, shoulders, and hips caused by internal bleeding in the affected joint. When a person with hemophilia B is injured, he or she does not bleed harder or faster than a person without hemophilia, but rather he or she bleeds for a longer time. Small cuts or surface bruises are usually not a problem, but more-traumatic injuries may result in serious problems, such as hemorrhage, anemia, and "bleeding episodes."
Hemophilia B is usually inherited, or passed down, from parents. Because hemophilia can be inherited, the risk of disease increases in closely related families. In about 30% of cases, however, there is no family history of the disorder and the condition is the result of a spontaneous gene mutation. Approximately 1 in 25,000 people worldwide are born with hemophilia B. All races are affected equally.
Currently, there is no known cure for hemophilia B. If treated properly, however, patients can live normal, healthy lives. Patients may receive clotting factor replacement therapy to restore the function of the missing clotting factor IX.
Bleeding, bruising, Christmas disease, coagulation, factor IX, factor IX hemophilia, haemophilia, haemophilia B, hemophilia, hematuria, hematochezia, hemorrhage, X-linked.
types of the disease
Severe: Patients with severe hemophilia B have less than 1% of normal factor IX activity. About 50% of people with hemophilia B have the severe form of the disease. These patients are at risk for spontaneous hemorrhages, often into the joints and muscles. Injuries may cause fatal bleeding to occur.
Moderate: People with moderate hemophilia B have 1 to 5% of normal factor IX activity. This type usually is diagnosed in children aged 1 to 2 years and accounts for 30% of all cases. These people may have occasional bleeding episodes without obvious causes.
Mild: Individuals with mild hemophilia B have greater than 5% of normal factor IX activity, and account for about 20% of all cases. These patients are at low risk for spontaneous bleeding but may bleed excessively following serious injury or surgery. In many cases, mild hemophilia is not discovered until an injury, surgery, or tooth extraction results in unusual bleeding. Mild hemophilia B may not be apparent or problematic until adulthood.