Hemophilia B is sometimes referred to as Christmas disease because a young boy named Stephen Christmas was the first patient that was recognized to have this form of hemophilia. There are several types of hemophilia and all are diseases that cause problems with blood clotting. Christmas disease is characterized by insufficient amounts of a blood-clotting plasma protein called factor IX. It is a hereditary condition caused by a recessive gene on the X chromosome; females who have another X chromosome that is likely to prevent the recessive gene from expressing, may therefore be carriers of this disease and not exhibit any symptoms. Hemophilia B is much more prevalent in males who do not have a second X chromosome to protect them from the recessive gene that causes it.
Women who are carriers of the recessive gene that causes Christmas disease have a 50-percent chance of passing the gene on to both their sons and daughters since they contribute one X chromosome to their children. Boys who inherit the gene from their mothers will always have the disease because the Y chromosome does not prevent the gene from expressing. A boy cannot inherit the disease from his father since he only receives a Y chromosome from his father. Girls inherit an X chromosome from both their mothers and their fathers, so they will develop the disease only if they inherit the gene from both parents, and will simply be carriers if they inherit the gene from only one parent. Women with hemophilia B will always pass the gene on to their children since both of their X chromosomes have the gene, and men with hemophilia B will always pass the gene on to their daughters since their only X chromosome carries the gene.
The severity of Christmas disease usually depends on how much factor IX is present in the blood. If levels of factor IX are extremely low, patients may experience spontaneous bleeding for no apparent reason. Patients whose levels are slightly to moderately low may bleed excessively only following injury or surgery. Symptoms of severe hemophilia are generally easier to detect and typically include heavy bruising, swollen or painful joints, bloody urine or stool, nosebleeds, and prolonged bleeding following trauma or injury. People with mild hemophilia may not exhibit symptoms until undergoing a dental procedure or surgery that causes profuse bleeding.
Christmas disease is treated by supplementing a patient's blood with factor IX concentrates. These concentrates may be administered at home on an as-needed basis whenever a patient begins to bleed, or they may be prescribed by physicians and dentists prior to certain procedures to prevent heavy bleeding. People who have severe hemophilia B may need to be treated with factor IX concentrates regularly as a preventative measure.
With treatment, people afflicted with Christmas disease generally can lead relatively normal lives. There is some risk of health complications caused by excessive bleeding, however, including joint damage and intracerebral hemorrhage. Other risks associated with Christmas disease include contracting hepatitis B due to frequent exposure to blood products, developing thrombosis following treatment, and developing inhibitors of factor IX which can render treatment ineffective.