Complete deletion of factor IX gene and inhibition of factor IX activity in a Labrador Retriever with hemophilia B

Hemophilia B is a clinically severe, heritable bleeding disorder found in many purebred and mixed-breed dogs. The condition is caused by deficiency of coagulation factor IX activity, and treatment involves transfusion to replace factor IX. Factor IX replacement may result in development of factor IX inhibitors. Risk for this complication appears to be greatest for hemophiliacs having large or complete factor IX gene deletions. Molecular characterization of genetic disorders has implications for treatment, in addition to facilitating disease reduction through genetic counseling.