The most severe form of von Willebrand disease, with virtual absence of von Willebrand factor (vWF) and severe haemorrhagic diathesis. Affected homozygotes present spontaneous bleeding or bleeding after trauma/surgery that can be life-threatening. It is inherited in an autosomal recessive manner through mutations in the VWF gene that differ by breed: Shetland Sheepdog, Scottish Terrier and Kooikerhondje.

Affected breeds: Nederlandse Kooikerhondje, Scottish Terrier, Shetland Sheepdog and Havanese (2025); it has also been described in the Dachshund. Carrier frequencies vary by breed and population; limited data.

- Prolonged bleeding after surgery, blood draws or trauma\n- Spontaneous mucocutaneous bleeding: epistaxis, gingivorrhagia\n- Easy bruising and ecchymoses\n- Gastrointestinal or urinary bleeding\n- Risk of severe, potentially fatal bleeding in homozygotes

Canine vWD was clinically typed in the 1980s-1990s. Rieger et al. (1998) identified the Kooikerhondje mutation and Venta et al. (2000) that of the Scottish Terrier; the Shetland Sheepdog variant comes from a US patent (not from peer-reviewed literature). In 2025 a new variant was described in the Havanese.

- Test breeding animals with the breed-specific genetic test\n- Do not mate two carriers: 25 % risk of affected homozygotes with severe bleeding\n- A carrier may be mated to a clear animal; offspring intended for breeding must be tested\n- Exclude affected animals from breeding\n- Before any surgery or whelping, test and provide for blood products/desmopressin according to the phenotype

Differential diagnosis with haemophilias A and B and with thrombocytopathies. Measurement of vWF:Ag quantifies the defect. Desmopressin (DDAVP) can transiently raise vWF in some carriers, but its effect is minimal or absent in type 3 homozygotes, where cryoprecipitate or fresh frozen plasma is required. The Shetland Sheepdog variant comes from a patent (not peer-reviewed); interpret that test with caution.

1. Rieger M et al. (1998) Identification of mutations in the canine von Willebrand factor gene associated with type III von Willebrand disease. Thromb Haemost 80(2):332-337. PMID: 9716162
2. Venta PJ et al. (2000) Mutation causing von Willebrand's disease in Scottish Terriers. J Vet Intern Med 14(1):10-19. PMID: 10668811
3. Armas-Jimenez AC et al. (2025) A VWF missense variant in Havanese dogs with type 3 von Willebrand disease. Anim Genet 56:e70021. PMID: 40504041
4. OMIA:001058-9615 (Von Willebrand disease III). La variante del Shetland sheepdog deriva de la patente US6074832A (no revisada por pares).