Hemophilia B in German Wirehaired Pointers

Hemophilia B is an inherited bleeding disorder caused by specific deficiency of coagulation Factor IX (Factor 9).  In addition to German Wirehaired Pointers (GWPs), Hemophilia B has been identified in more than 25 different breeds and in mixed breed dogs.  Severely affected dogs have recurrent and potentially fatal bleeds into chest, abdomen, joints, or muscles.  Hemophilia B in GWPs, however, is relatively mild.  Affected dogs have shown signs of lameness and swollen joints after strenuous exercise, prolonged bleeding from minor wounds, and hemorrhagic complications after surgery.  Although Hemophilia B impacts on quality of life and performance, virtually all affected dogs survive to adulthood.  

Hemophilia B is a sex-linked, recessive trait.  The Factor IX gene is carried on the X chromosome.  All males (XY) have a single X chromosome, inherited from their dam.  If that X chromosome carries a mutant gene, the male is affected with hemophilia.  All females (XX) inherit one X-chromosome from dam and one from sire.  If a female inherits a mutant gene, from either parent, she is a carrier of hemophilia.  Carrier females appear clinically normal and do NOT express a bleeding tendency.

Carrier detection is based on a direct DNA test.  DNA is isolated from a blood sample and a specific portion of the Factor IX gene is then amplified and scored to detect the presence (or absence) of a unique Factor IX mutation.  Hemophilia B carrier females have one copy of the mutant sequence and one copy of the normal Factor IX gene sequence.  Clear females have two copies of the normal Factor IX gene sequence.  DNA analysis can differentiate affected males from clear males, however coagulation Factor IX assays can accurately (and more rapidly) define a male's genetic status.

For additional information, visit http://www.diaglab.vet.cornell.edu/coag/test/hemopwh.asp or call 607-275-0622.