Genetic basis of Bernard-Soulier Syndrome in Cocker Spaniels - is caused by a large deletion mutation in the GP9 gene, which encodes a subunit of the platelet surface membrane glycoprotein complex. This glycoprotein complex functions as the receptor for von Willebrand factor (vWF), critical for platelet adhesion and normal blood clotting. The identified mutation is a 2460 base pair deletion in exon 1 of the GP9 gene on dog chromosome 20, resulting in a frameshift and premature stop codon, truncating almost two-thirds of the encoded protein. BSS is inherited in an autosomal recessive manner, meaning affected dogs have two copies of the mutated gene; carriers with one copy are asymptomatic but can pass the mutation to offspring. Genetic testing is available to diagnose affected dogs and identify carriers to guide breeding programs.
Pathophysiology - The mutation causes a defect in platelet adhesion due to the absence or dysfunction of the GP9 platelet glycoprotein. This causes impaired interaction with von Willebrand factor, leading to defective blood clot formation. Affected dogs have macrothrombocytopenia (abnormally low platelet count with unusually large platelets). This defect leads to prolonged bleeding times and the tendency to develop large bruises and hematomas after trauma.
Complications - Clinical signs usually present from birth up to 2 to 4 years of age but may become more apparent with trauma. Symptoms include: Nosebleeds (epistaxis), Gingival bleeding, Hematuria (blood in urine), Bleeding after mating, whelping, or surgery, Formation of large hematomas and bruising after minor injuries or venipuncture. Bleeding episodes can be severe and lifelong but may remain stable over time.
Why This Matters to Breeders and Vets - For breeders, identifying carriers through genetic testing is crucial to avoid breeding two carriers, which would produce affected puppies with a 25% risk per litter. Avoiding carrier-to-carrier matings can ultimately reduce or eliminate BSS from the breed population. For veterinarians, recognizing signs of BSS helps differentiate it from other bleeding disorders, guiding appropriate diagnosis and management. Genetic diagnosis helps prevent misdiagnosis and inappropriate treatment. Dogs with BSS can maintain a good quality of life with careful management.
Summary - Bernard-Soulier Syndrome (Cocker Spaniel Type) is a severe inherited bleeding disorder caused by an autosomal recessive deletion in the GP9 gene, leading to defective platelet adhesion, macrothrombocytopenia, and lifelong bleeding tendencies. Clinical signs include nosebleeds, bruising, and prolonged bleeding after injury or surgery, typically appearing in early life but can worsen with trauma. Genetic testing enables diagnosis, carrier identification, and informed breeding decisions to prevent affected puppies and manage the disease in the breed population.