What is von Willebrand’s disease?
Von Willebrand’s disease (VWD) is an inherited bleeding disorder that is very rare in cats, but relatively common in dogs and humans. It is caused by a deficiency in a protein called von Willebrand factor (VWF), which is essential for blood clotting. Von Willebrand factor helps platelets (the blood cells used in clotting) to stick together and form clots to seal broken blood vessels. Affected cats have normal platelets, but they have clotting difficulties because their platelets cannot properly attach to injury sites.
What are the clinical signs of VWD?
The clinical signs of VWD are similar to those of any clotting disorder: abnormal or unexpected bleeding. Affected cats often bleed from their mucous membranes (e.g., mouth and nose). You may notice that they intermittently sneeze blood or they have visible blood in the saliva (bleeding gums). Blood may also be observed in the urine or feces.
VWD is often first suspected when a cat bleeds excessively after surgery or trauma (e.g., physical injuries, giving birth). Although some degree of bleeding is normal in these situations, a cat with VWD will continue bleeding for an abnormally long time.
How is VWD diagnosed?
Your veterinarian will first take a complete medical history and perform a thorough physical examination of your cat. This assessment will help suggest possible causes of your cat’s difficulties and rule out other medical conditions.
Next, your veterinarian will perform laboratory tests. These tests will likely include a complete blood cell count (CBC), blood chemistry profile, and a urinalysis. In most cats with VWD, all bloodwork will be normal. In some cases, especially if a cat has experienced a recent bleeding event, the CBC may show anemia due to red blood cell loss.
Your veterinarian may also perform coagulation tests to assess your cat’s blood clotting. Most coagulation tests show normal results in cats with VWD. To diagnose VWD, your veterinarian must run a specific test that assesses the concentration of von Willebrand factor in the bloodstream. Low levels of von Willebrand factor confirm a diagnosis of VWD.
How will my veterinarian treat VWD?
The only treatment for VWD is to supplement or replace von Willebrand factor in the bloodstream. There is no treatment currently available that forces the body to create its own von Willebrand factor, so this supplementation must be repeated, as needed, when cats are in crisis or when bleeding is expected.
A blood transfusion may be performed, especially if your cat is experiencing severe anemia due to blood loss. In a blood transfusion, your cat receives all blood components, including von Willebrand factor, other clotting factors, and replacement red blood cells.
Other materials, such as fresh frozen plasma (cryoprecipitate) may also be used in the treatment of VWD. With these products, only a portion of the donor’s blood is delivered to your pet. Your pet will receive von Willebrand factor and other clotting factors, but no additional red blood cells.
These therapies are often used before surgery in a cat with known VWD. Increasing the blood levels of von Willebrand factor decreases the likelihood of abnormal bleeding during surgery and recovery.
What is the prognosis for VWD?
Most cats with mild to moderate VWD will experience a good quality of life and require no medical treatment.
Some cats are more severely affected. These cats may require blood transfusions for excessive bleeding, which may occur spontaneously or following surgery. In these cats, physical activity may carry additional risks of injury, so you may need to restrict their activity levels. Additionally, these cats will need to be closely monitored over the course of their lifespan. However, with proper care, even severely affected cats can live relatively normal lives.
