Hemophilia B, also known as Christmas disease, is a bleeding disorder due to factor IX deficiency. It is less common than hemophilia A and is also an X-linked autosomal recessive disorder that occurs most commonly in males.

Hemophilia B is characterized by prolonged bleeding following injuries, surgical procedures, and dental extractions. It can present with variable phenotypes. In a small percentage of female carriers, it may present in a milder form. Onset depends on severity of phenotype, but bleeding episodes may begin in early childhood and adolescence. More severe forms frequently present with spontaneous hemorrhage. Left untreated, hemophilia B may be fatal (intracranial hemorrhage) or result in severe motor impairment or paralysis (chronic joint disease).

Rarely, hemophilic pseudotumors may result from destruction of bone at sites of repeated bleeding. They may cause swelling and restricted movement.

Related topic: hemophilia A