How Is The Inherited Bleeding Disorder Von Willebrand Disease Passed On? What Is The Risk Of Giving It To A Child?

People who live with this disease frequently suffer from nosebleeds that start spontaneously, without warning. These heavy nosebleeds don't just last more than 10 minutes, they may also be so hard to stop that they require medical attention and cauterization. These people bruise so easily that their loved ones may begin to wonder if they're being assaulted, even if they're not especially physically active.

If they're women, they'll have scarily heavy menstrual periods and such an abundant flow that the CDC (not especially famous for its hyperbole) describes it as "flooding". Sometimes, they'll have large amounts of blood in their stool.

If they're actually injured, the bleeding patients with this disease experience can go on for extraordinary amounts of time. If they need surgery, they can easily hemorrhage, and even after bleeding was successfully stopped, it can begin again at any time during the recovery period.

You will probably have heard of hemophilia, while remaining completely ignorant about the fact that Von Willebrand disease affects over three million people in the United States alone, or around one in every 100 people. Yet, this common genetic disorder affects every aspect of patients' lives, and can in rare cases even prove to be fatal. 

If you love someone with Von Willebrand disease, however, or you have the bleeding disorder yourself, you will want to know more about the risk of passing it on.

What Is Von Willebrand Disease?

Von Willebrand disease is the most common inherited bleeding disorders — bleeding disorders being, as the name suggests, conditions that lead patients to bleed more easily than normal, and for whom stopping the bleeding is also harder. This is the result of a problem during the blood clotting process, which would normally cause the body to "plug" smaller bleeds quite easily through the process of coagulation. Other fairly common bleeding disorders, some of which are better known, include hemophilia A, hemophilia B, thrombotic thrombocytopenic purpura, and Glanzmann disease.

Healthy blood hosts numerous proteins that assist in the blood clotting process after injury, and a phenomenon called the coagulation cascade ensures that we do not bleed to death. The so-called von Willebrand factor is one of these. In people living with von Willebrand disease, this protein either works incorrectly or is almost entirely lacking. Because the von Willebrand factor helps platelets to form clots that stem bleeding, this means that people with von Willebrand disease keep bleeding for longer, in extreme cases leading to life-threatening and even fatal situations. 

Around one in 100 people is affected by von Willebrand disease, which strikes men and women in equal numbers. Because women of reproductive age experience menstruation, however, they are more likely to notice that something is wrong sooner when they suffer from extremely heavy periods. 

Three distinct types of von Willebrand disease exist:

• In Type 1 von Willebrand disease, which is the most common type, patients have some von Willebrand factor, but below average amounts. Some also have lower levels of other proteins important to the blood clotting process. Type 1 von Willebrand represents the majority of all cases, or about 85 percent.
• People who have Type 2 von Willebrand disease produce von Willebrand factor in normal amounts, but the protein does not work as it should. The size, timing, or attachment process can be faulty, leading to delays in blood clotting.
• Type 3 von Willebrand disease causes patients to have no von Willebrand factor at all, or extremely low levels. They also lack Factor VIII, another protein essential to the blood clotting process. 

How Are Types 1 and 2 of von Willebrand Disease Inherited?

Cases of Type 1 von Willebrand disease are, along with most cases of Type 2, inherited in an autosomal dominant pattern. This means that a child born to one parent with von Willebrand disease will inherit the condition if the von Willebrand disease allele is passed on, and both parents do not need to carry the genetic changes that would lead to the bleeding disorder.

In concrete terms:

• If one parent has von Willebrand disease, while the other does not carry the gene, there is a 50 percent chance that the resulting child will have Type 1 or 2 von Willebrand disease. There is also a 50 percent chance that the child will not have von Willebrand disease.
• If both parents have the genetic changes that cause von Willebrand disease, there is a 50 percent chance that the child will be born with the condition.
• There is also, however, a 25 percent risk that a child born to two parents with von Willebrand disease will suffer from a more severe form of the disease. Similarly, there is a 25 percent chance that the child will not be affected by the condition at all.

How Is Type 3 von Willebrand Disease Inherited?

Type 3 von Willebrand disease has an autosomal recessive inheritance pattern. This means that parents who are not affected by von Willebrand disease themselves, but who carry the allele — or genetic code, if you prefer — that contains the information that causes this condition can still pass von Willebrand disease on to a child. 

If both parents have the von Willebrand disease allele, but do not have the condition themselves, they have a 50 percent chance of having a child who carries the allele but is not affected by the disease. They have a 25 percent chance of having a child who does not carry the allele at all, as well, but also a 25 percent risk of having a child who has Type 3 von Willebrand disease. 

This is how people for whom von Willebrand disease runs in the family can pass the bleeding disorder on, potentially without ever knowing that the condition ran in either of the partners' families. 

In couples where one parent has Type 3 von Willebrand disease but the other does not carry the allele, on the other hand, all children will have the allele — and none will have the disorder. 

Because this disorder can present as anything from a nuisance to a life-threatening or fatal disease, gene counseling options are being explored for people with von Willebrand disease. With gene therapy, it might be possible to prevent passing the allele that lead to von Willebrand disease onto children. 

In the meantime, for people who do have the disease, timely diagnosis can help to prevent numerous complications. Medications, including those that deliver the missing von Willebrand factor to the affected patient's body, can help to stop bleeds before they become dangerous. Lifestyle changes can reduce the risk of serious bleeds, while in women, contraceptives can eliminate the extremely heavy periods associated with von Willebrand disease.