Genetic basis - Caused by a missense mutation (c.731G>A) in exon 7 of the F9 gene, which encodes coagulation Factor IX essential for blood clotting. The mutation results in a glycine to glutamic acid substitution (G244E) in the catalytic domain of Factor IX, causing a nonfunctional protein. The disorder is inherited in an X-linked recessive manner since the F9 gene is on the X chromosome. Males with the mutation on their one X chromosome are affected; females are carriers if heterozygous and affected only if homozygous (very rare).
Pathophysiology - Mutation leads to deficiency or absence of Factor IX activity, impairing the coagulation cascade causing prolonged or spontaneous bleeding. Blood does not clot properly, increasing risk of hemorrhage even after minor injuries or surgeries.
Complications - Clinical signs include easy bruising, spontaneous bleeding, bleeding from the nose or mouth, large hematomas, joint bleeding (hemarthrosis), and prolonged bleeding after surgery or trauma. Severity ranges from mild to life-threatening bleeding. Without treatment, dogs can bleed to death after injuries or surgical procedures.
Why This Matters to Breeders and Vets - Prevents propagation of severe, inherited bleeding disorders improving breed health and welfare. Assists veterinarians in early diagnosis and management of bleeding. Educates breeders and owners on X-linked recessive inheritance and risks. Improves prognosis and survival with early identification and treatment.