Hemophilia B

Alternative names:

Christmas disease; factor IX hemophilia

Definition:

A hereditary blood coagulation disorder caused by a deficiency of a plasma protein called factor IX that affects the clotting property of blood.

Causes, incidence, and risk factors:

Hemophilia is a group of hereditary bleeding disorders of specific blood clotting factors classified as hemophilia A and B. Hemophilia A is 7 times more common than hemophilia B. Hemophilia B is the result of a deficiency of clotting factor IX. The disorder is caused by an inherited sex-linked recessive trait with the defective gene located on the X chromosome. Females are carriers of this trait. Fifty percent of the male offspring of female carriers will have the disease, and 50% of their female offspring will be carriers. All female children of a male hemophiliac will be carriers of the trait.

The severity of symptoms can vary with this disease, and the severe forms become apparent early on. Bleeding is the hallmark of the disease and typically occurs if an infant is circumcised. Additional bleeding manifestations make their appearance when the infant becomes mobile. Mild cases may go unnoticed until later in life, when they occur in response to surgery or trauma. Internal bleeding may occur anywhere and bleeding into joints is common. Risk factors are a family history of bleeding and being male. The incidence of hemophilia B is 1 out of 50,000 men.