von Willebrand Disease
The most commonly inherited bleeding disorder is von Willebrand Disease (vWd) and occurs in both males and females.
What is von Willebrand Factor?
Von Willebrand Factor (vWF) is a clotting protein in the blood. It is produced in the cells that line the blood vessels and then is released into the blood stream.
Bleeding occurs when blood vessels are injured. Platelets, a type of blood cell, stick to the injured vessel and form a platelet plug. Von Willebrand factor acts as a glue to help the platelets stick to the injury site. Simultaneously, other clotting proteins work together to form a clot, further sealing the area of damage.
How does someone get von Willebrand Disease?
Von Willebrand Disease is known as an inherited or genetic disorder meaning it is passed down through families through information in the cells called genes.
What are the signs and symptoms of von Willebrand Disease?
Von Willebrand Disease (vWD) can be a mild disorder associated with few, if any, symptoms. Sometimes people are not diagnosed until they have excessive bleeding following a serious injury, accident, (invasive) dental work, or surgery. In other cases, diagnosis of one family member may lead to a diagnosis in other family members as well.
Bleeding usually involves the mucous membranes, the delicate tissues that line such body passages as the nose, mouth, uterus, vagina, stomach and intestines. Some of the usual symptoms of vWD include frequent nosebleeds, easy bruising, heavy menstrual flow, and excessive bleeding following surgery, childbirth, or dental work.
How is it diagnosed?
vWD may be difficult disorder to diagnose. It is often hard to distinguish individuals with mild vWD from those without. Children whose symptoms are fairly mild may live for many years without a diagnosis or perhaps may never be diagnosed. It may also be hard to distinguish between vWD and other bleeding disorders.
Laboratory tests are an important part of diagnosis. Repeat testing is often necessary in order to get a clear answer.
The tests most frequently performed in people who might have vWD are:
- Platelet Function Analyzer (PFA-100): measures how well the platelets stick together to form a clot
- Factor VIII activity -- measures how much factor VIII is present in your child's blood
- Ristocetin cofactor activity -- tests how well vWF works
- vWF Antigen: measures how much vWF protein is present in your child's blood whether or not it works properly
- Multimer analysis -- examines the structure of vWF molecules
Types of von Willebrand Disease
Type I: The von Willebrand factor is deficient in quantity. This type is the most common form of the disease.
Type II: The von Willebrand factor is deficient and does not function normally.
Type IIA - vWF does not form proper multimers.
Type IIB – vWF multimers are too active and bind to platelets in the blood, resulting in removal of platelets and vWF from the blood.
Type IIM – vWF does not bind to platelets well.
Type IIN – vWF does not bind to factor VIII well.
Type III: There is an absence of von Willebrand factor in the blood. An associated low level of coagulation factor VIII also occurs. This type is the most severe form of the disease.
Treatment
The treatment goal of von Willebrand Disease is to normalize the level of vWd factor and clotting factor VIII in the blood, allowing for routine blood clotting. Treatment is based on the type and severity of disease. If your child only has bruising or nosebleeds, medications may not be necessary. Serious bleeding issues may require more sophisticated treatment including:
Cryoprecipitate
Cryoprecipitate is a fraction of human plasma, the liquid part of blood. It contains both factor VIII and von Willebrand factor. If cryoprecipitate is obtained from a well-screened unaffected family member or donor, it may be a viable treatment option. However, in general the Medical and Scientific Advisory council of the National Hemophilia Foundation no longer recommends this treatment method due to its associated risks.
Desmopressin (DDAVP)
DDAVP is a synthetic hormone used to stimulate the release of von Willebrand factor and factor VIII found in storage sites of cells that line the blood vessels. Desmopressin can be given by vein, subcutaneously, or in the form of a nasal spray. DDAVP does offer convenient treatment for some vWd patients, but unfortunately it does not work effectively in all von Willebrand patients. Tests can be performed to see whether your child adequately responds to this type of therapy.
Factor VIII Concentrates
Alphanate and Humate P (factor VIII) replacement products contain von Willebrand factor and are suitable for treating von Willebrand disease. These concentrates have been purified to reduce the risk of blood-borne viruses. However, not all types of factor VIII products are appropriate for treating von Willebrand disease, because not all factor VIII concentrates contain von Willebrand factor.
Rev. 3/07
