Von Willebrand factor (VWF) is a protein in the blood crucial for blood clotting. Low or dysfunctional VWF leads to Von Willebrand Disease (VWD), a bleeding disorder. VWD impairs the body’s ability to stop bleeding effectively.
The Role of Von Willebrand Factor
Von Willebrand factor serves two primary functions in blood clotting. First, it helps platelets adhere to the site of an injury. When a blood vessel is damaged, VWF acts like a bridge, allowing platelets to stick to the exposed vessel wall and to each other, forming a preliminary plug.
The protein also acts as a carrier for another clotting protein, Factor VIII (FVIII). VWF protects FVIII from premature breakdown, ensuring sufficient levels are available for the later stages of the clotting cascade. Without adequate or functional VWF, both platelet adhesion and FVIII stability are compromised, leading to impaired clot formation and prolonged bleeding.
Recognizing the Signs of Low VWF
Low Von Willebrand factor levels, characteristic of Von Willebrand Disease, often cause various bleeding symptoms. One common sign is easy bruising, where even minor impacts can result in noticeable bruises. Individuals may also experience frequent, prolonged nosebleeds.
Bleeding from the gums is another indicator, and prolonged bleeding after minor cuts, surgery, or dental work is also common. For individuals who menstruate, heavy or prolonged menstrual bleeding, known as menorrhagia, is a frequent symptom. This can include needing to change sanitary protection more than once an hour or experiencing periods that last longer than seven days. These bleeding issues occur because the impaired function of VWF prevents the rapid and stable formation of blood clots.
Causes and Different Forms
Low Von Willebrand factor is most often an inherited condition, passed down through families due to a genetic variant in the VWF gene. This gene provides instructions for making the Von Willebrand factor protein. The way it is inherited can vary; for instance, the most severe type, Type 3, occurs when a child inherits the gene from both parents.
Von Willebrand Disease is categorized into three main types based on the quantity and quality of VWF. Type 1 is the most common, accounting for about 70-75% of cases, where the body produces lower-than-normal amounts of functional VWF, leading to mild bleeding symptoms.
Type 2, comprising about 15-25% of cases, involves normal or near-normal amounts of VWF, but the protein does not function correctly due to structural or functional defects. This type has several subtypes (2A, 2B, 2M, 2N), each with specific functional issues.
Type 3 is the rarest and most severe form, affecting less than 5% of individuals, where the body produces very little or no VWF, resulting in a higher risk of severe bleeding, including internal bleeding. Less commonly, low VWF can be acquired later in life due to other medical conditions, such as autoimmune diseases or certain cancers, or from specific medications.
Diagnosis and Treatment Approaches
Diagnosis of low Von Willebrand factor begins with a thorough review of an individual’s personal and family bleeding history. Healthcare providers will inquire about past bleeding episodes, their severity, and any family members with similar issues.
Specific blood tests then measure various aspects of VWF. These tests include the VWF antigen test (which determines the amount of VWF protein present) and VWF activity tests (which assess how well the VWF is functioning), such as the ristocetin cofactor activity (VWF:RCo). Factor VIII levels are also measured, as VWF carries and protects this clotting protein. Diagnosis can sometimes be complex, especially in mild cases, as VWF levels can fluctuate.
Treatment for low VWF is tailored to the individual’s specific type and severity of Von Willebrand Disease and the nature of the bleeding event. One common medication is desmopressin (DDAVP), a synthetic hormone that stimulates the body to release more stored VWF. Desmopressin is used for Type 1 and some Type 2 forms, and a trial dose may be given to assess its effectiveness.
For individuals who do not respond to desmopressin or have more severe forms, VWF replacement therapy may be used. This involves infusions of concentrated blood-clotting factors that contain both VWF and Factor VIII. Other treatments include anti-fibrinolytic drugs, which help stabilize blood clots and prevent their premature breakdown, useful for bleeding in mucous membranes like the mouth or uterus. Oral contraceptives can also be prescribed to manage heavy menstrual bleeding.