Von Willebrand disease is the most common inherited blood disorder that prevents blood from clotting properly. The condition arises from issues with a protein called von Willebrand factor (VWF), where individuals either have a low level of this protein or the protein does not function correctly. While most people are born with the disorder, its signs may not become apparent for many years.
The Role of von Willebrand Factor
When a blood vessel is injured, von Willebrand factor acts like a glue, binding to the vessel wall and catching circulating platelets. This process helps platelets stick to the injury and each other, forming an initial plug that stops the bleeding. This function is important in areas of high blood flow, such as in narrow arteries.
VWF also serves as a protective carrier for another clotting protein, factor VIII. In the bloodstream, factor VIII is vulnerable to breaking down, but VWF binds to it, forming a complex that shields it from degradation. This ensures enough factor VIII is transported to an injury to help form a stable blood clot.
Classifications of von Willebrand Disease
Inherited Von Willebrand disease is categorized into three main types. Type 1 is the most common and mildest form, where individuals have a reduced quantity of VWF in their blood, but the protein they do have functions normally. The levels of VWF for those with Type 1 are between 20% to 50% of the normal range.
Type 2 VWD is characterized by a defect in the function of the VWF protein, even though the amount of the protein may be normal. This type is divided into several subtypes, including 2A, 2B, 2M, and 2N, each corresponding to a specific functional problem with the protein. Symptoms associated with Type 2 are often mild to moderate.
Type 3 VWD is the rarest and most severe form. People with Type 3 have very little or no VWF in their bloodstream, which leads to significant bleeding problems. It is also possible to develop acquired von Willebrand disease later in life, which is a non-inherited form associated with other medical conditions.
Signs and Symptoms
The signs of Von Willebrand disease vary depending on the type and severity of the condition. Many individuals with milder forms may not realize they have the disorder because their symptoms are minor or absent. One of the most common indicators is frequent nosebleeds that last longer than 10 minutes and are difficult to stop.
Other common signs include:
- Easy or lumpy bruising from minor bumps or injuries.
- Prolonged bleeding after a minor cut, a dental procedure, or surgery.
- Heavy or extended menstrual periods (menorrhagia) for women.
- Blood in the urine or stool.
Diagnosis and Management
Diagnosing Von Willebrand disease starts with a review of a person’s personal and family medical history, focusing on past bleeding issues. If VWD is suspected, a doctor will order specialized blood tests to confirm the diagnosis. One such test, the VWF antigen assay, measures the amount of VWF protein present in the blood.
Another test is the VWF activity assay, often called the Ristocetin Cofactor activity test, which assesses how well the VWF protein is functioning. Doctors also measure the activity level of factor VIII, since VWF is its carrier protein. Analyzing the results of these tests together helps a physician determine if a person has VWD and which specific type they have.
Management of VWD focuses on controlling and preventing bleeding episodes. For milder forms like Type 1, a medication called desmopressin (DDAVP) is used to stimulate the body to release its stored VWF and factor VIII. For more severe types or for major bleeding, replacement therapies are used, which involve intravenous infusions of concentrated VWF and factor VIII. Other medications, known as antifibrinolytics, can also be prescribed to help prevent the breakdown of blood clots.