Types of von Willebrand Disease
There are three main types of VWD, numbered 1, 2, and 3. Type 2 has several subtypes. Each of these is described below. It is important for a person with VWD to know which type he or she has.
Type 1 von Willebrand Disease
Type 1 VWD is the most common type. About 85% of the people with VWD have this type. In Type 1 VWD, there is not enough von Willebrand factor (VWF) in the bloodstream. The VWF works correctly but the body needs more of it to adequately control bleeding. Since VWF protects factor VIII from being destroyed, a low level of VWF may also mean a lower level of factor VIII. A small number of people with Type 1 VWD can have severe bleeding at times.
Type 2 von Willebrand Disease
Type 2 VWD is the next most common type. About 15% of people with VWD have Type 2. They usually have more severe bleeding problems than people with Type 1. In Type 2 VWD, there is enough von Willebrand factor but it does not work right. This may be caused by the VWF protein being the wrong size. The VWF protein is made up of parts called multimers. For the VWF to do its job, the body must put these multimers together correctly.
Type 2 VWD has four subtypes A, B, M, and N:
In Type 2A, the VWF multimers are not the right size. This stops the platelets from making a good platelet plug.
In Type 2B, the VWF multimers are not the right size and the VWF becomes too active. It attaches to the platelets in the blood when it is not supposed to. The body quickly gets rid of the platelets with the attached VWF. This causes a shortage of both platelets and VWF in the blood.
In Type 2M, the VWF is not able to stick to the platelets and a good platelet plug does not form.
In Type 2N, the VWF is not able to do its job as the carrier and protector of factor VIII. The level of factor VIII in the body is low because it doesn’t have the VWF to keep it from being broken down. With low levels of factor VIII, the body has trouble making a fibrin clot. A person with Type 2N VWD can appear to have mild hemophilia with some of the same symptoms. It is not hemophilia, though, because the problem is with the VWF and not the factor VIII. Another name for Type 2N is Type 2 Normandy because it was first described in patients from the Normandy region in France.
Type 3 von Willebrand Disease
Type 3 is the rarest type of VWD. About one person in a million has it. Type 3 also has the most severe symptoms. People with Type 3 VWD have little or no VWF in their blood. Without VWF to act as a carrier, the amount of factor VIII in the blood also drops to low levels. People with Type 3 VWD have trouble making both a platelet plug and a fibrin clot. They can have bleeding into their joints and muscles without even knowing they have injured themselves. These people also have frequent bleeding from their noses and mouths. Women with Type 3 VWD have long menstrual periods with very heavy bleeding. Because the symptoms are so severe, Type 3 VWD is almost always diagnosed when someone is very young.