vWDI is inherited in an autosomal dominant manner with incomplete penetrance, in the Kromfohrländer breed

One Health: Animal Models of Heritable Human Bleeding Diseases

Animal models of human and animal diseases have long been used as the lynchpin of experimental and clinical research. With the discovery and implementation of novel molecular and nano-technologies, cellular research now has advanced to assessing signal transduction pathways, gene editing, and gene therapies. The contribution of heritable animal models to human and animal health as related to hemostasis is reviewed and updated with the advent of gene editing, recombinant and gene therapies.

Investigation of a common canine factor VII deficiency variant in dogs with unexplained bleeding on autopsy

The factor VII (FVII) protein is an integral component of the extrinsic coagulation pathway. Deleterious variants in the gene encoding this protein can result in factor VII deficiency (FVIID), a bleeding disorder characterized by abnormal (slowed) clotting with a wide range of severity, from asymptomatic to life-threatening. In canids, a single FVIID-associated variant, first described in Beagles, has been observed in 24 breeds and mixed-breed dogs. Because this variant is present in breeds of diverse backgrounds, we hypothesized that it could be a contributing factor to unexplained bleeding observed in some canine autopsy cases. DNA was extracted from paraffin-embedded tissue samples from 67 anticoagulant-negative autopsy cases with unexplained etiology for gross lesions of hemorrhage. Each dog was genotyped for the c.407G>A (F71) variant. Experimental controls included 3 known heterozygotes and 2 known homozygotes for the F71 variant, 2 normal dogs with known homozygous wild-type genotypes (F7WF7W), and 5 dogs with bleeding at autopsy that tested positive for anticoagulant rodenticide and were genotyped as F7WF7W. All 67 cases tested homozygous for the wild-type allele, indicating that the common FVIID variant was not responsible for the observed unexplained bleeding. Our work demonstrates the usefulness of retrospective studies utilizing veterinary diagnostic laboratory databases and tissue archives for genetic studies. In the case of FVIID, our results suggest that a singular molecular test for the F71 variant is not a high-yield addition to postmortem screening in these scenarios.

Case report of unilateral retrobulbar hematoma associated with von Willebrand disease in a Doberman Pinscher dog

A 5-year-old Doberman Pinscher dog was presented with sudden onset left-sided periocular bleeding following third eyelid gland replacement surgery. Left-sided exophthalmos and 360-degrees subconjunctival hemorrhage were present. The ophthalmic examination revealed blindness with absent direct and consensual pupillary light reflexes. A superficial exposure ulcerative keratitis due to exophthalmos was also present. Computed tomography (CT) revealed a large left-sided retrobulbar mass lesion surrounding the optic nerve, compatible with a retrobulbar hematoma. Due to absence of orbital fractures and no history of trauma, a coagulopathy was strongly suspected. The buccal mucosal bleeding time (BMBT) was prolonged (>4 minutes) consistent with a primary hemostatic defect in the absence of thrombocytopenia. Von Willebrand factor antigens levels were decreased (24%- Normal Range: 50%-150%). Surgical drainage of the retrobulbar hematoma was performed uneventfully thirty minutes after subcutaneous injection of desmopressine acetate, Minirin® (1 µg/kg, SC). Von Willebrand disease type I gene mutation was confirmed by PCR amplification of the DNA encoding von Willebrand factor. This case report demonstrates that hemostatic disorders, including von Willebrand Disease (vWD), are a risk factor for orbital bleeding following surgical trauma. Retrobulbar hematoma should be considered as a differential diagnosis in any dog with exophthalmos.