von Willebrand's Disease, type 1

Von Willebrand’s Disease Type 1 is the most common bleeding disorder in dogs and is considered the mildest form of vWD. Because clotting ability corresponds to the level of von Willebrand’s factor present, severity of clinical signs in affected dogs vary widely. Dogs with this genetic variant may appear asymptomatic, display only mild signs, or show frequent and severe signs of abnormal clotting. Age of onset can vary with some affected dogs displaying signs later in life. Additionally, illness, estrus, or pregnancy may exacerbate clinical signs in affected dogs. Clinical signs may include bruising easily, bleeding after losing baby teeth or chewing on toys, excessive bleeding from trauma, injury or surgery, nosebleeds and other forms of spontaneous bleeding. Please note that subclinical cases can also be associated with increased bleeding after surgery or trauma. An affected dog will have a normal PT/aPTT but may demonstrate prolonged bleeding during functional testing, such as buccal mucosal bleed time (BMBT). However, performing von Willebrand’s factor testing at a reference laboratory is considered necessary to confirm diagnosis and to determine the concentration of vW factor present within an individual

Medications known to interfere with clotting, such as non-steroidal anti-inflammatory drugs (NSAIDs) and certain antibiotics, should be avoided. Some dogs may exhibit temporary improvement when treated with desmopressin acetate (DDAVP) or blood products, particularly when given prior to necessary surgical procedures. In most cases, therapy is limited to supportive care (which can include transfusions if needed) and avoiding non-crucial surgical procedures. Based on findings in humans with vWD, minimizing stressful events can also be considered as emotional stress may worsen clinical signs.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This condition is considered autosomal dominant with incomplete penetrance, meaning not all dogs with one copy will show clinical signs and dogs with two copies are considered at highest risk for being diagnosed with vWD. Diagnosing vWD is performed through reference laboratory testing of the dog’s blood levels of von Willebrand factor. A dog with the vWD Type 1 genetic variant with normal blood levels of von Willebrand factor as tested by a reference laboratory can be safely bred with a clear dog with no copies of the vWD Type 1 variant. Puppies in a litter expected to contain carriers should be screened before breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note that the estrus cycle and pregnancy can lead to further fluctuation in the von Willebrand factor in females which may exacerbate clinical signs. Additionally, it is possible that disease signs similar to the ones caused by the vWD Type 1 variant could develop due to a different genetic or clinical cause.