Christmas Disease Christmas disease, also called hemophilia B or factor IX hemophilia, is a rare genetic disorder in which your blood doesn’t clot properly. If you have Christmas disease, your body produces little or no factor IX. This leads to prolonged or spontaneous bleeding. The less factor IX your body produces, the worse your symptoms are. Without treatment, Christmas disease can be fatal.
How Is Christmas Disease Inherited?
The gene responsible for Christmas disease is carried on the X chromosome. Females have two X chromosomes and males have one X and one Y chromosome. If a male inherits the faulty gene on his X chromosome, he could develop Christmas disease. If a female inherits the faulty gene on one of her X chromosomes, she’ll be a carrier for Christmas disease and may pass the defective gene on to her children.
All daughters of a father who has the defective gene will be Christmas disease carriers. A father doesn’t pass the faulty gene on to his sons. A mother who carries the faulty gene has a 50 percent chance of having a son with Christmas disease and a 50 percent chance of having a daughter who’s a carrier of the disease.
Genetic Testing for Christmas Disease
If you’re a woman with a family history of Christmas disease, you can have genetic testing to see if you carry the faulty gene. Genetic testing is a very accurate way to detect the faulty gene.