A group of hereditary disorders characterized by prolonged bleeding and
sometimes excessive bleeding. There may be bleeding into joints,
gastrointestinal tract, and urinary tract. On laboratory the activated partial
thromboplastin (PTT) time is prolonged. However, the prothrombin time (PT) and
bleeding time are normal.
Hemophilia A and hemophilia B (Christmas disease) account for most cases of
hemophilia. Hemophilia A is caused by a lack of the blood clotting protein
factor VIII, and hemophilia B is caused by a lack of the blood clotting protein
factor IX. Hemophilia A is 7 times more common than hemophilia B. Both diseases
are caused by a defective gene located on the X chromosome.
Since the male contributes the X chromosome to form female and the Y chromosome
to form male offspring, all the daughters of a male affected with hemophilia
will be carriers of the defective gene. The daughters of a hemophiliac male
will pass the gene to 50% of their male offspring who in turn will have
For the newborn at risk for hemophilia it is best to avoid fetal scalp
electrodes, forceps, and vacuum extraction. The pediatrician should be notified
of the baby's possible hemophilia. Circumcision, if desired, should be delayed
as well as intramuscular injections until coagulation studies are completed and
the diagnosis of hemophilia is either established or ruled out.