Hemophilia A (also spelt Haemophilia A) is a blood clotting disorder caused by a mutation of the Factor VIII gene. See hemophilia.
Hemophilia B (also spelt Haemophilia B) is a blood clotting disorder caused by a mutation of the Factor IX gene. See haemophilia. It is sometimes called Christmas disease, named after the first patient to contract it.
A mild form of hemophilia that mainly occurs in Jews of Ashkenazi descent. It is due to deficiency of coagulation factor XI. Treatment is usually not necessary, except in relation to operations.