Von Willebrand disease
Von Willebrand disease
What is von Willebrand disease?
Von Willebrand disease (vWD) is a lifelong bleeding disorder caused by a defect or deficiency of a blood-clotting protein called von Willebrand factor. Von Willebrand factor is a protein that works in the initial stages of blood clotting. This glue-like protein interacts with blood cells called platelets to form a plug, which prevents the blood from flowing at the site of injury. People with vWD are unable to make this plug because they do not have enough von Willebrand factor or their factor is abnormal.
This genetic disease can be inherited from either parent and affects males and females equally. Von Willebrand disease is the most common bleeding disorder and is estimated to occur in one to two percent of the population
Von Willebrand disease is classified by type:
- Type I. This is the most common and mildest form of vWD. Levels of von Willebrand factor are lower than normal and levels of factor 8 (another type of clotting factor in the blood) also may be reduced.
- Type II. In children with Type II vWD, the von Willebrand factor itself has an abnormality. Depending on the abnormality, the patient may be classified as having Type IIa or Type IIb vWD. In Type IIa, the level of von Willebrand factor is reduced, as is the ability of platelets to clump together. In Type IIb, although the factor itself is defective, the ability of platelets to clump together is actually increased.
- Type III. This is severe vWD. These people may have a total absence of von Willebrand factor, and factor 8 levels often are less than 10% of normal.
VWD types I and II usually are inherited in what is known as a "dominant" pattern. This means that if even one parent has the gene and passes it to a child, the child will have the disorder.
VWD type III, however, usually is inherited in a "recessive" pattern. This type occurs when the child inherits the gene from both parents. Even if both parents have mild or asymptomatic disease, their children are likely to be severely affected.
What are the symptoms of von Willebrand disease?
Von Willebrand disease can be a mild disorder and often children have very few symptoms. Recurrent nosebleeds are a common complaint in children with vWD. Usually, children with vWD bruise easily, or bleed after tooth extraction, tonsillectomy or other surgery. Females can have increased menstrual bleeding. A person's symptoms may change throughout their life, but the type of vWD does not change.
How is von Willebrand disease diagnosed?
Von Willebrand disease can be difficult to diagnose. This is partly because the results of a person's blood tests can vary day-to-day. For example, the amount of von Willebrand factor can be temporarily increased when a child/teen:
- Is under stress.
- Has an infection.
- Has recently undergone surgery.
- Has recently undergone a blood transfusion.
Also, people with blood type O have lower levels of von Willebrand factor. All of these reasons can make a test inconclusive. That's why repeat testing often is needed in order to obtain a correct diagnosis.
Several different types of blood tests are needed to make the diagnosis. These include bleeding time, Factor 8 activity, Ristocetin cofactor activity, vWF antigen, multimer analysis and Ristocetin–induced platelet aggregation. The reason that many lab tests are needed to diagnose vWD is because of the multiple types of vWD. Analysis of all the lab results will help the hematologist determine which type of vWD is occurring.
How is von Willebrand disease treated?
The treatment for a child with von Willebrand disease will depend on the type of vWD and the severity of symptoms.
If a child has a nosebleed, pinching the bridge of the nose for ten to fifteen minutes can often stop it. Once a clot is formed, antifibrinolytic medications such as Amicar may be used to keep the clot in place longer.
For more serious bleeding, Stimate, given intravenously, or desmopressin acetate (DDAVP), given via nasal spray, is the treatment of choice when a child has been diagnosed with mild von Willebrand disease. Stimate or DDAVP are used to boost the child's own factor 8 and von Willebrand factor levels. These medications may be given to increase the amount of the von Willebrand factor long enough for surgery or dental procedures to be performed.
For excessive bleeding, infusions of a concentrated form of factor 8, which is rich in von Willebrand factor, may be required. Examples of this type of factor include Humate-P®, Alphanate® or Koate DVI®. These medications can be injected through a vein.
About treatment for von Willebrand disease at Children's
Children's cancer and blood disorders program achieves outcomes that rank among the top national programs and cares for more than two-thirds of Minnesota children and adolescents with blood disorders. Care for von Willebrand disease is provided through a division of the cancer and blood disorders program called the Center for Bleeding and Clotting Disorders. Through the center, families have access to the newest and most promising treatments and receive care spearheaded and coordinated by a board-certified hematologist/oncologist.
If you are a family member looking for a Children's hematologist or oncologist or wanting to schedule an appointment, please call our clinic at Children's – Minneapolis at (612) 813-5940.
If you are a health professional looking for consultation or referral information, please call Children's Physician Access at 1-866-755-2121 (toll-free) and ask for the on-call hematologist/oncologist.