von Willebrand Disease (vWD) is the most common inherited bleeding disorder. It is an inherited disorder of von Willebrand factor (vWF), which is a protein found in the blood that is important in the process of blood clotting. It is inherited by both boys and girls but is more often diagnosed in girls.
vWF has two important jobs in the body. It helps platelets (a type of blood cell) stick to injured areas of blood vessels, to help form a “platelet plug,” on which a blood clot can be built. It also helps to maintain the levels of factor VIII (a clotting protein that also plays an important role in forming blood clots) in the blood.
Single strands of vWF are bound together in different-sized clusters of the protein called “multimers” that circulate in the blood. The larger multimers are the most important for helping platelets bind to injured blood vessels.
There are different types of vWD, with each type having a different effect on the roles of vWF.
This is by far the most common type of vWD. In this type, a person’s body is only able to produce a fraction of the normal amount of vWF. Because there is less vWF to do its job, a person’s platelets do not stick to damaged blood vessels as well as they should, which can lead to an increase in bruising or bleeding. If a child is only able to make a small amount of vWF, then their levels of factor VIII may be lower than normal as well, so their blood does not clot normally, which can also lead to increased bruising and bleeding.
In this type, a person’s body can make good amounts of vWF, but there is some defect in the vWF that is made so that it does not work as well. There are different subtypes:
As in type 1, the person’s body cannot make normal levels of vWF. However, in this type their body cannot make any vWF, so their platelets do not bind an injured blood vessel normally and their factor VIII levels in the blood are significantly lower than normal.
A person inherits vWD from either one or both of their parents. Type 1 is an autosomal dominant disorder, meaning it is inherited from one parent. Type 3 is autosomal recessive, meaning a person must inherit one gene from each parent in order have the disorder.
vWD is diagnosed with a set of special blood tests that are typically performed because a child has some bleeding or bruising that is suspicious for a bleeding disorder and they have a family history of vWD. The common tests that are performed include:
The bleeding symptoms experienced are variable; they may be mild or severe and depend upon which function of vWF is affected. If children have a type in which platelet binding is affected, then they typically have mucocutaneous bleeding. This means they have bleeding involving the mucosal surfaces of the body, including nasal passages (nose bleeds), mouth (gum bleeding) and lining of the uterus (heavy or prolonged menstrual periods as they get older and bleeding after childbirth). They also can have cutaneous (skin) bleeding (more and bigger bruises than normal).
In those types in which factor VIII levels are lower than normal, the person can have bleeding into their deep soft tissues (large bruises that can be felt), and if the factor VIII levels are particularly low, they can have hemarthrosis (bleeding into the joints).
Some are unfortunate to have both defective platelet binding and low factor VIII levels (particularly those with type 3) and may experience many different bleeding symptoms.
People with the most common type of vWD, type 1, can have symptoms that range from relatively mild to severe. Many boys with type 1 vWD are not diagnosed, as their symptoms may be limited to bruising and nose bleeds. On the other hand, due to the common symptoms of heavy and prolonged periods as they mature, more young women than young men appear to be diagnosed with vWD.
Fortunately, there are safe and effective treatments available for all types of vWD. They can be used either to treat bleeding episodes when they occur or prevent bleeding from planned surgeries, dental procedures or physical activities.