Alternative Names factor IX deficiency, Christmas disease
Definition Haemophilia B is an inherited bleeding disorder affecting mostly men. This disease interferes with the blood's ability to clot.
What is going on in the body? In haemophilia B the blood does not clot well. This is caused by a deficiency of a blood protein that helps form blood clots, called factor IX. Bleeding can be in any part of the body. It can be external or internal. Most of the time the disease shows up early in life. This condition can be life threatening. Haemophilia B is very similar to haemophilia A but is less common.
What are the signs and symptoms of the disease? Problems usually start in early childhood. Severe cases will cause:
In someone with mild haemophilia, excessive bleeding may occur only with injury or surgery.
What are the causes and risks of the disease? People with this condition are usually males who inherit an abnormal X chromosome from the mother. Because women have 2 different X-chromosomes, they usually do not get the disease. It is unclear why the genetic defect occurs. The exact nature of the genetic defect can vary. That is why there is a range of severity of the disease.
What can be done to prevent the disease? Haemophilia B is a genetic disease. The disease cannot be prevented in a person who is born with this gene. Genetic screening can tell individuals if they are carriers of the disease. Since haemophilia B is a treatable disease, genetic counselling before or during pregnancy can be helpful to couples with a family history of the disease.
An unborn foetus can also be tested for haemophilia. The testing can be done as early as the first trimester, with chorionic villi sampling or amniocentesis. These tests carry a small risk of causing a miscarriage.
How is the disease diagnosed? Haemophilia B is diagnosed by measuring factor IX protein activity in the plasma. The severity of the disorder is closely linked to factor IX activity. An individual with mild disease has more factor IX activity than those with severe disease. Other tests that may be used in diagnosis include the partial thromboplastin time, or PTT, and thrombin time, or PT. These laboratory tests measure the clotting ability of the blood.
What are the long-term effects of the disease? Long term effects of haemophilia B are usually only seen with moderate to severe disease. Possibilities include:
bleeding into the brain, resulting in strokes and mental disabilities
damage from bleeding. This includes joint deformity, arthritis, and muscle stiffness.
abnormal iron deposits in the liver and other organs, which may cause damage
What are the risks to others? This is not a contagious disease. Someone with haemophilia or a family history of haemophilia may find genetic counselling helpful. This will determine the risk of passing on the abnormal gene to the children or grandchildren.
What are the treatments for the disease? An individual who develops bleeding problems needs to be treated regardless of the severity of the disease. Although fresh frozen plasma was used in the past, factor IX concentrate has been the standard of care for many years. This is purified, treated, concentrated human plasma that is high in factor IX activity. An individual's dose of factor IX and the duration of treatment are based on several factors. This includes the baseline factor IX activity level, total body weight, severity of bleeding, and site of bleeding. Someone with internal bleeding or central nervous system bleeding is treated more aggressively.
Factor IX is given by slow, intravenous infusion. A person can do this at home. A person who requires frequent infusions often has a central line surgically implanted. This is a catheter that goes into one of the large veins, and provides a painless way to give the factor IX. Serious haemorrhage may require treatment in the hospital.
Some persons have immune system problems that make haemophilia B worse. These persons may require treatment with medications to suppress the immune system.
Chronic joint deformity due to haemophilia is becoming less common. However, some individuals require operations for joint problems. The most common sites for surgery include the weight bearing bones of the hips and knees.
What are the side effects of the treatments? Too much infusion of factor IX can cause blood clots to form in the veins. Medication to suppress the immune system can make the person more susceptible to infections.
Before current screening procedures, a factor IX transfusion carried a risk of HIV or hepatitis. Currently, with present screening techniques for factor IX products, the risk of acquiring hepatitis and HIV is very low. Individuals who have only been receiving blood products in the past 10 years have a very low risk of acquiring hepatitis and HIV from factor IX products.
What happens after treatment for the disease? A person with haemophilia B is often tested after treatment to measure how effective the factor IX infusion has been. The site of bleeding may complicate this evaluation.
How is the disease monitored? Periodic testing of factor IX levels may be used to help assess the response to treatment. It also can determine when another treatment is necessary. Monitoring may also require special x-ray tests, surgery, or other blood tests.
Author: Thomas Fisher, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
