Von Willebrand disease (VWD) is genetic in the vast majority of cases. It is caused by changes in the VWF gene, located on chromosome 12, which provides instructions for making a protein essential for blood clotting. The condition affects up to 1% of the general population and occurs with equal frequency in men and women.
That said, not every case traces back to an inherited gene. A small number of people develop an acquired form later in life due to other medical conditions. Understanding which type you’re dealing with, and how it passes through families, matters for both treatment and family planning.
How the VWF Gene Affects Clotting
The VWF gene tells your body how to produce von Willebrand factor, a protein that acts like molecular glue at the site of a blood vessel injury. When a vessel is damaged, von Willebrand factor latches onto the exposed tissue and then grabs passing platelets from the bloodstream, slowing them down so they can stick and form a clot. This initial catch is brief on its own, but it buys enough time for other receptors on the platelet surface to lock in and create a stable seal.
When the VWF gene carries a mutation, the protein it produces may be reduced in quantity, structurally abnormal, or completely absent. The result is that platelets can’t anchor properly at wound sites, leading to prolonged or excessive bleeding.
Inheritance Patterns by Type
VWD comes in three main types, and each follows a slightly different genetic path.
Type 1 and Most Type 2
These are typically autosomal dominant, meaning a single altered copy of the VWF gene is enough to cause the disorder. If one parent carries the mutation, each child has a 50% chance of inheriting it. Type 1 is the mildest and most common form, involving lower-than-normal levels of an otherwise functional protein. Type 2 involves a protein that doesn’t work correctly, even if levels appear adequate.
Type 2 Subtypes
Type 2 is further divided into several variants based on what exactly goes wrong with the protein. In type 2A, the largest and most effective forms of the protein are either broken down too quickly or never assembled properly. In type 2B, the protein binds too aggressively to platelets while they’re still circulating, which paradoxically depletes both the protein and the platelets before they’re needed at a wound. Type 2M produces a protein that simply can’t grip platelets well. Type 2N creates a protein that fails to carry and protect clotting factor VIII, a partner protein it normally stabilizes in the bloodstream. Some cases of type 2 follow a recessive pattern rather than a dominant one, requiring mutations from both parents.
Type 3
Type 3 is the most severe form. People with type 3 have very little or no detectable von Willebrand factor. It is classically described as autosomal recessive, meaning a child must inherit a defective copy from each parent to develop the full condition. In this scenario, parents are carriers who typically have no symptoms themselves.
However, research on Canadian families with type 3 VWD found that in roughly half of families, the inheritance pattern was actually co-dominant. That means even carriers (people with just one mutated copy) had low protein levels and experienced bleeding symptoms, rather than being completely unaffected. This complicates the traditional view that carriers are always symptom-free.
Can VWD Appear Without Family History?
Yes, though it’s uncommon. New (de novo) mutations in the VWF gene have been documented in both type 1 and type 2 VWD. In these cases, neither parent carries the mutation. The genetic change occurs spontaneously either during the formation of the egg or sperm, or very early in embryonic development.
More often, what looks like a new case actually reflects unrecognized disease in the family. VWD symptoms vary widely, even among relatives who share the same mutation. A parent might carry the gene but never have experienced a situation that triggered noticeable bleeding, such as surgery or childbirth. Some family members may have been mislabeled as simply “easy bruisers” without ever receiving a diagnosis. Reduced penetrance (where the gene is present but doesn’t always produce obvious symptoms) and variable expressivity (where the same mutation causes mild problems in one person and significant bleeding in another) both contribute to this pattern.
Acquired Von Willebrand Syndrome
Not all cases of von Willebrand deficiency are genetic. Acquired von Willebrand syndrome (AvWS) develops later in life in people with no personal or family history of bleeding problems. It produces similar symptoms but arises from other medical conditions that interfere with the protein after it’s been made normally.
The most common associations are cardiovascular conditions like aortic valve stenosis and mechanical heart pumps (left ventricular assist devices). In these situations, the physical shearing forces of turbulent blood flow physically tear apart the largest, most effective forms of von Willebrand factor. Blood cancers, particularly those involving abnormal immune proteins like multiple myeloma and a precursor condition called MGUS, can also trigger the syndrome when antibodies attack the protein or when abnormal cells absorb it from the bloodstream. Autoimmune diseases such as lupus and even hypothyroidism (where decreased thyroid function reduces protein production) are additional causes. In the case of hypothyroidism, treating the thyroid condition with thyroid hormone replacement can reverse the bleeding problem entirely.
When Genetic Testing Helps
Most VWD is diagnosed through blood tests that measure how much von Willebrand factor you have and how well it functions. Genetic testing of the VWF gene isn’t needed for every patient, but it becomes valuable in specific situations. These include distinguishing type 2N VWD from hemophilia A (since both involve low factor VIII but require different management), telling type 2B apart from a similar platelet disorder, and providing prenatal diagnosis for families with type 3 VWD.
Genetic analysis is also useful when someone has a more severe presentation of type 1 disease and standard lab tests don’t fully explain the picture. For family planning, identifying the exact mutation in an affected person allows relatives to be tested and given clearer information about their own risk and the risk of passing VWD to children.
Risk of Passing VWD to Children
For dominant forms (type 1 and most type 2), one affected parent means each pregnancy carries a 50% chance of the child inheriting the condition. The severity can vary, though. A parent with mild type 1 may have a child whose symptoms are noticeably different, either milder or more pronounced, due to other genetic and environmental factors.
For recessive forms (type 3 and some type 2), both parents must carry a mutated copy. When two carriers have a child, there is a 25% chance the child will have the full disease, a 50% chance the child will be a carrier, and a 25% chance the child will inherit no mutations at all. Given the emerging evidence that carriers of type 3 mutations are not always asymptomatic, even carrier status may be worth identifying.