Hemophilia 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 hemophilia 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. Hemophilia B is very similar to hemophilia A but is less common.

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.