von Willebrand Disease

About von Willebrand Disease

Von Willebrand disease, or vWD, is an inherited disorder that affects the blood's ability to clot properly. It takes its name from Dr. Erik von Willebrand, who first described the condition in 1926. 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.

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 vWD have a problem with one or both of these blood components.

Types of von Willebrand Disease

As with many conditions, there are various forms of vWD. Type 1 is the most common and the mildest form of the disease. Unlike hemophilia, which affects only boys, vWD affects boys and girls equally.

• In Type 1, the level of von Willebrand factor in the blood is reduced. Although the condition can be made worse by taking aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), the symptoms might be so mild that the person isn't ever diagnosed. People with Type I vWD usually do not bleed spontaneously but can have significant bleeding with trauma, surgery, or when they have a tooth pulled.
• In Type 2, the von Willebrand factor has an abnormality. Within this type are two kinds of 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, leading to clumping of the platelets, which can cause a low platelet number
    
    Other type 2 subtypes exist, but are much rarer.
• 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, or platelet-type, von Willebrand disease is similar to Type 2B, but the defect is in the platelets instead of in the factor.

Causes of vWD

Like hemophilia, vWD is a genetic disorder that is passed from parent to child. 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.

Signs and Symptoms

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
• excessive or prolonged bleeding after circumcision

Diagnosis and Treatment

Because the symptoms can be mild, vWD can be difficult to diagnose and often goes undetected.

Tests to diagnose vWD may include:

• 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 and von Willebrand activity (ristocetin cofactor or RCF). The disorder is considered mild if a person has 20% to 49% of the normal amount. It is severe if the amount is 5% or less. Patients with type O blood may have reduced levels of von Willebrand factors.
• von Willebrand multimers test, which helps to classify the type of von Willebrand disease
• platelet function tests, which determine how well the platelets work

Tests may need to be done more than once because these levels may rise and fall over time in an individual. Also, the doctor will take a family medical history to see if other relatives have a bleeding disorder.

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

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

Medication to inhibit the breakdown of blood clots also might be used, such as aminocaproic acid (Amicar).

Precautions

Kids with vWD should avoid unnecessary trauma, including contact sports. If bleeding does occur, apply pressure to the area. During nosebleeds, pinch the end of the nose and have the child lean slightly forward to keep the blood from flowing down the throat.

Because of the possibility of excessive bleeding, male infants who are at risk for vWD (those with a family history of the disease) should not be circumcised without a doctor's OK.

Girls with vWD who have started their periods might want to take extra pads or a change of clothes in case of accidents. Heavy menstrual bleeding can sometimes be controlled with birth control pills.

Call your doctor immediately if your child experiences any excessive or unexplained bleeding.

Reviewed by: Gregory C. Griffin, MD
Date reviewed: May 2010