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What is von Willebrand Disease?

von Willebrand disease, or vWD, is an inherited disorder that impacts the blood's ability to clot properly. As a group, bleeding disorders (including hemophilia) are rare. von Willebrand disease is the most common inherited bleeding disorder, affecting as much as 1% of the population or more. Unlike hemophilia, which affects only boys, vWD affects boys and girls equally. The child of a man or a woman with vWD has a 50% chance of getting the gene. In types 1 and 2, a child inherits the gene for the disease from one parent. In type 3, the child usually inherits the gene from both parents. In those cases, the child will likely have severe symptoms, even if the parents don't have any symptoms at all.

Normally, bleeding occurs when a blood vessel is cut or torn. Platelets (small cells that float in the blood) plug the hole in the blood vessel to stop the flow of blood. With the help of calcium, vitamin K, and a protein called fibrinogen, the platelets create a mesh to hold the plug in place and close the wound. As this mesh dries, it hardens and forms a scab to protect the wound as it heals. A substance in the blood known as von Willebrand factor helps platelets stick to damaged blood vessels. Another function of von Willebrand factor is to carry the important clotting protein, called factor VIII, in the blood. People with von Willebrand disease have a problem with one or both of these blood components.

Types of von Willebrand Disease

Type 1

• Most common and the mildest form of vWD
• The level of von Willebrand factor in the blood is reduced
• The condition can be made worse by taking aspirin and other nonsteroidal anti-inflammatory drugs
• Generally spontaneous bleeding does not occur
• Can have significant bleeding with trauma, surgery, or when a tooth pulled

Type 2

• The von Willebrand factor has an abnormality
• There are two kinds of Type 2 vWD:
  - Type 2A, in which the building blocks that make up the factor (called multimers) are smaller than usual or break down too easily.
  - Type 2B, in which the factor sticks to the platelets too well. This leads to clumping of the platelets, which can cause a low platelet number.
• Type 3 patients have severe bleeding problems and have very low von Willebrand factor and factor VIII (the protein that helps with blood clotting).

Pseudo (platelet-type)

• Similar to Type 2B, but the defect is in the platelets instead of in the factor.

Signs and Symptoms of von Willebrand Disease

The symptoms of von Willebrand disease may include:

• Bruising that's unusual in location or frequency
• Abnormal menstrual bleeding
• Bleeding in the mucous membranes, such as the gums, nose, and lining of the gastrointestinal system
• Excessive or prolonged bleeding after a tooth is pulled or tonsils are removed or prolonged oozing from cuts

Diagnosis

Because symptoms can be mild, vWD can be difficult to diagnose and often goes undetected. The tests to diagnose vWD may include:

• Bleeding time
• Factor VIII level test (also called factor VIII coagulant) - which measures the level of factor VIII and its ability to function
• von Willebrand factor antigen test (also called factor VIII antigen) - which measures the amount of von Willebrand factor. The disorder is considered mild if levels are 20% to 40% of the normal amount. It is severe if the amount is less than 10% of normal.
• Ristocetin cofactor activity test (also called factor VIII ristocetin cofactor) - which measures how well the von Willebrand factor is working
• von Willebrand factor multimers test - which aids in classifying the type of vWD
• Platelet function tests - which determine how well the platelets work and help identify the type of vWD or the presence of another disorder

These tests may need to be repeated more than once because these levels may rise and fall over time in an individual.

Treatment

The most common treatment for von Willebrand disease is desmopressin. This medication causes a temporary increase in the von Willebrand levels. It can be given intravenously or intranasally (into the nose), but may be ineffective in Type 2A or Type 2B.

Patients with Type 3 (and some with Type 2A and 2B) will need treatment with a product such as Humate P, a medication derived from human plasma that contains both factor VIII and von Willebrand factor. This medication is given intravenously (into the vein). Patients with Type 1 may also require the use of this medication in certain situations, such as major trauma or major surgery, although they can generally be treated with desmopressin.

For additional information:
Project Red Flag - www.projectredflag.org/common_questions/what_is_von_willebrand.htm
The National Hemophilia Foundation - www.hemophilia.org/bdi/bdi_types3.htm
OBGYN.net Publications - www.obgyn.net/english/pubs/announcements/vwd_q_a.htm