Types of von Willebrand disease
- What are the different types of von Willebrand disease?
- What is Type 1 VWD?
- What is Type 2 von Willebrand disease?
- What is Type 3 von Willebrand disease?
What are the different types of von Willebrand disease?
What is Type 1 VWD?
Type 1 VWD is the most common form, accounting for 75% of all cases of VWD. In Type 1 VWD, the von Willebrand factor (VWF) works normally, but there is not enough of it.
Many people with Type 1 VWD have no symptoms at all until they experience a bad injury or an operation. Then, they could have serious bleeding.
Others have mild symptoms such as:
• minor bruises
• bleeding from the nose and gums
• prolonged bleeding from cuts.
During their periods, some women with Type 1 VWD have heavy, abnormally long bleeding, called menorrhagia. This can have a major effect on health and quality of life.
Injuries and surgery can lead to severe bleeding even in this mild form of VWD. That’s why it’s important for people who think they might have VWD to get tested.
What is Type 2 von Willebrand disease?
Type 2 VWD is less common than Type 1. It represents 20-25% of all cases.
In Type 2 VWD, the amount of VWF in people’s blood is often normal. The problem is that the VWF does not work properly.
There are several sub-types of Type 2 VWD. It is important to get an exact diagnosis because the sub-types are treated differently.
Type 2A VWD is the most common sub-type. It represents 15-20% of all cases of VWD. In Type 2A VWD, the amount of VWF is often normal. However, because of a defect in the VWF protein, the platelets do not bind together well. The VWF does not act as a glue to hold the platelets in place to plug a hole in a blood vessel.
Type 2B VWD is the next most common. It represents about 5% of all cases of VWD. In Type 2B VWD, the VWF binds to platelets in the bloodstream, instead of binding at the site of the injury to the blood vessel. Then, the body removes these large bundles of platelets from circulation. This causes a shortage of platelets.
Type 2N VWD is much rarer. (The “N” stands for Normandy, France where the sub-type was first identified.) This is what doctors know about it.
• In Type 2N the VWF works normally with platelets. As a result, the grouping of platelets around the injury happens as it should.
• VWF also helps to carry around factor VIII in the blood and stabilize it so it can take part in the formation of a solid clot. In Type 2N the VWF does not transport factor VIII. As a result, factor VIII levels are low.
• Sometimes, because of the low factor VIII levels, Type 2N is mistaken for factor VIII deficiency hemophilia.
• In order for a child to get Type 2N, both parents must pass on the defective gene.
There are several other extremely rare sub-types of Type 2 VWD, including Type 2M. The 'M' stands for 'Multimer', a part of the structure of the VWF molecule. In Type 2M, binding of the VWF to platelets is impaired.
What is Type 3 von Willebrand disease?
Type 3 VWD is very rare. It affects about 1 in 500,000 people. However, it is the most severe type of VWD. People with Type 3 VWD have very little VWF in their blood. Because VWF transports factor VIII, they also have very low levels of factor VIII. As a result, bleeding can happen often and, if untreated, can be serious.
Usually, in order for a baby to get Type 3 VWD, both parents must pass on the defective VWD gene. However, in some cases, the disease can result from a combination of one parent passing on the defective gene and a mutation in the child's gene inherited from the other parent.