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Postoperative haemorrhage due to P2Y12 receptor defect (Greater Swiss Mountain Dog)

Hematológico · Dog

Hereditary thrombopathy of the Greater Swiss Mountain Dog caused by a mutation in the P2RY12 gene, which encodes the platelet ADP receptor. Platelets from affected animals do not respond to ADP and therefore do not aggregate properly after activation. Homozygous dogs present mild spontaneous bleeding, but the serious risk appears after surgery or trauma, when the haemorrhage can be exsanguinating and fatal. It is the first P2RY12 gene defect described in a domestic species and constitutes the natural model of the equivalent human disorder (platelet disorder type 8).

Inheritance pattern	Autosomal recessive. Most dogs with severe bleeding are homozygous, but a heterozygote with severe postoperative bleeding has been described, so carriers may also be at risk.
Gene / Mutation	P2RY12 c.516_518del (p.Ser173del); 3-base-pair deletion that removes a serine from the extracellular domain
Penetrance	In homozygotes the response to ADP is abolished, but spontaneous bleeding may be mild or absent; the severe haemorrhagic phenotype depends largely on the trigger (surgery or trauma). In heterozygotes the risk is low but not nil: a carrier (heterozygote) with severe postoperative bleeding and platelet aggregation abolished in response to ADP has been documented.
Code	qbgp
Turnaround time	15 days
Price	52,60 €

Incidence

Affected breed: Greater Swiss Mountain Dog. The mutant allele is relatively widespread in the breed ("widespread", Flores et al., 2017), although no reliable carrier frequency figures from large series have been published; it has not been detected in other breeds.

Breeder management

- Test Greater Swiss Mountain Dog breeding animals with the P2RY12 test before the first mating\n- Do not mate two carriers: 25 % risk of affected homozygotes; also avoid mating an affected homozygote with a carrier\n- A carrier may be mated to a clear animal; the offspring intended for breeding should be tested\n- ALWAYS inform the veterinarian before any scheduled surgery (including neutering/spaying) of the animal's P2RY12 status, even if it is a carrier, and have blood products and desmopressin available\n- Consider the animal's status before tooth extraction and minor dental procedures\n- Exclude affected homozygous animals from breeding

Specialist notes

Differential diagnosis with von Willebrand disease (the most common in dogs with postoperative bleeding) and with the thrombopathies of other breeds (e.g., GP defect in the Basset Hound, thrombasthenia in the Ottoman Shepherd). The distinguishing feature: normal platelets, PT, APTT and vWF, but abolished ADP aggregation. Flow cytometry with fibrinogen-FITC and ADP is decisive. Remember that a dog with prolonged BMBT and normal coagulation warrants suspicion of a thrombopathy. The mechanism by which a heterozygote may bleed is not clarified by the available sources.

References

1. Boudreaux MK, Martin M (2011). P2Y12 receptor gene mutation associated with postoperative hemorrhage in a Greater Swiss Mountain dog. Vet Clin Pathol 40(2):202-206. PMID: 21554368
2. Flores RS et al. (2017). Heterozygosity for P2Y12 receptor gene mutation associated with postoperative hemorrhage in a Greater Swiss Mountain dog. Vet Clin Pathol 46(4):569-574. PMID: 28800150
3. OMIA:001564-9615. Bleeding disorder, P2RY12-related in Canis lupus familiaris (dog).

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