Von Willebrand Disease in Dogs

Case Example

Physical Exam

You get a call from a distressed client- her dog Captain has a nosebleed that will not stop bleeding.

You have an appointment available and tell her to bring him right away.

Bloodwork

CBC:

Anemic

Normal platelet count!

Coagulation test:

Normal PT and aPTT

Next step?

Bloodwork

Aside from the nosebleed, Captain looks and sounds healthy.

Based on the breed and presentation, do you have any differentials? What will you do next?

Physical Exam

Diagnosis

Findings

To confirm vWD, you send a sample of Captain's blood to the lab for a vWF antigen assay.

-measures the exact amount of vWF in the blood.

The results confirm your diagnosis of vWD.

Testing for vWF

Prolonged bleeding time found on buccal mucosal screening.

Next steps?

Von Willebrand Disease in Dogs

History:

Captain is a 2YO intact male Doberman Pinscher.

The nosebleed was spontaneous and began about one hour ago.

Captain arrives

Kate Wilson, Julia Berger, Madison Jagoda, Erica Falvey, Amber Leavis, Bri Bergen, Lionel Biggemann

Treatment

Pathophysiology

Clinical signs

Lab Findings

Genetics, Pathophysiology and Treatment of VWD

• Hemorrhage and excessive bleeding after surgery
• Most common sign is mucosal hemmorrage
• Increased bleeding during estrus
• Epistaxis, hematuria

• Anemia
• Prolonged activated clotting time
• Prolonged buccal mucosal bleeding time
• PT normal
• PTT sometimes prolonged

Pathophysiology

• Type 1 VWD: Deficiency in all multimers of vwf, bleeding severity is variable. Doberman Pinschers

• Type 2: Low concentration of high molecular weight vwf. Moderate to severe bleeding. German Pointers

• Type 3: Absence of all multimers of vwf. Most severe and affects many breeds.

Genetics

• All dogs have 2 copies of the vWF gene (1 from mother, 1 from father)

• In some breeds, having a single mutant copy is enough to cause abnormal bleeding (not seen in all individuals, though)

• 3 types of Von Willebrand Disease, 5 mutations identified in dogs

• Direct DNA tests available for all 5

• Type 1:
• Good prognosis. Recommend desmopressin to promote release of vWf and cryoprecipitate prior to surgery.
• Type 2 & 3:
• Mild to Guarded prognosis. May require transfusions for minor injuries throughout life. Monitor and limit activities

Pathophysiology

• Von Willebrand factor is a glycoprotein produced by megakaryocytes and endothelial cells.
• It helps platelet adhesion to the blood vessel wall.

Genetics

VWD Type 2 (VWD2) Inheritance

Genetics

VWD Type 3 (VWD3) Inheritance

Pathophysiology

• Autosomal recessive

• Point mutation
• Most common in Scotties, Shelties

Genetics "Take Home"

- AUTOSOMAL RECESSIVE

- Test dogs from suspect bloodlines!

- Make breeding decisions with results in mind

VWD Type 1 (VWD1) Inheritance

• The platelets then become activated and expose a fibrinogen binding site.
• Plasma vwf binds Factor VIII of the clotting cascade and prolongs it's half life. (Levels of this factor are reduced with vwd)

Pathophysiology

x

VWF

References

• https://ahdc.vet.cornell.edu/sects/coag/clinical/vonwill/inherit.cfm
• http://www.animalgenetics.us/Canine/Genetic_Disease/VWD1.asp
• http://www.questdiagnostics.com/testcenter/testguide.action?dc=CF_vWD
• https://www.vetgen.com

Avoid drugs that will affect clotting factors:

Heparin

Aspirin

Sulfa-based antibiotics

Penicillin

Antihistamines