Hemophilia A is a hereditary X-linked, recessive bleeding disorder found in many different canine breeds. Clinical signs of hemophilia include prolonged bleeding from minor wounds and internal hemorrhage involving joints, muscles, and other tissues, with no antecedent trauma. The defect appears to arise from frequent spontaneous mutations in the coagulation Factor VIII gene. Affected males are accurately diagnosed based on coagulation Factor VIII assays. In contrast, carrier females appear clinically normal and may have Factor VIII values that overlap those of clear females. Hemophilia A is often propagated when these asymptomatic carrier females are used for breeding.

Our laboratory is recruiting newly diagnosed cases of hemophilia A, and dogs related to previously tested hemophilic males and carrier females. Laboratory analyses will include measurement of Factor VIII coagulant activity (performed on citrate plasma) and DNA isolation (from EDTA whole blood) for Factor VIII mutation and marker genotyping. DNA markers represent normal variation in the Factor VIII gene sequence that can be used for linkage analysis of the hemophilia trait. Results and interpretation of males’ FVIII:C will be sent to participants within 3 to 4 days of sample receipt. Marker genotyping will be performed in batches every 2 to 3 weeks and results compiled within 1 month of sample receipt. This is a 2-year project funded by the Morris Animal Foundation.

Participation involves submission of a blood sample and pedigree from each enrolled dog. Participation is voluntary and a signed consent form is requested with sample submission. All information identifying individual dogs will remain confidential. Dogs are assigned a study number and data for all hemophilia-affected families will be summarized anonymously. Please call Dr. Brooks (607-275-0622) if you would like to participate or discuss the project in more detail.