Genetic basis - Haemophilia A in Rhodesian Ridgebacks is caused by a mutation in the F8 gene, which encodes coagulation Factor VIII, essential for normal blood clotting. A short interspersed nuclear element (SINE) insertion in exon 14 of the F8 gene is the specific mutation identified in affected Rhodesian Ridgebacks. The disorder is inherited as an X-linked recessive disease, located on the X chromosome. Males are mostly affected due to having one X chromosome; females must inherit two copies of the mutation to be affected but can be carriers if heterozygous
Pathophysiology - Mutation leads to lack or severely reduced activity of Factor VIII, impairing the blood clotting cascade. This results in inability to form stable blood clots, causing prolonged or spontaneous bleeding episodes.
Complications - Clinical signs include spontaneous internal bleeding, bleeding after injury or surgery, bleeding from mouth, subcutaneous and intramuscular hematomas, lameness, and joint hemorrhages (hemarthrosis). Excessive bleeding can be life-threatening without intervention. Diagnosis is often through prolonged activated partial thromboplastin time (aPTT) and reduced Factor VIII activity.
Why This Matters to Breeders and Vets - Prevents producing puppies with a severe bleeding disorder, safeguarding breed health and reducing suffering. Allows veterinarians to diagnose and manage bleeding disorders early through genetic and clinical tools. Educates breeders on inheritance patterns to make informed mating choices. Early identification and intervention improve quality of life and survival.