Von Willebrand disorder (VWD) is a bleeding disorder which affects the blood’s ability to clot. If your blood doesn’t clot, you can have bleeding symptoms. Some of the most common symptoms are easy bruising, frequent and prolonged nosebleeds, prolonged bleeding after some dental procedures, prolonged bleeding post-surgery or traumatic injury. For women, heavy or prolonged menstrual bleeding and prolonged bleeding after childbirth.
Your body makes lots of different clotting proteins that help you to stop bleeding, one of which is called von Willebrand factor (vWF). In vWD, either your body does not make enough vWF which can be referred to as a “quantitative” (i.e. not enough) problem or the vWF doesn’t work as well as it should which is referred to as a “qualitative”, (i.e not as effective). Bleeding happens when you damage a blood vessel. Normally, your body responds by fixing the damage in the blood vessel wall, stopping the bleeding. The body’s first response to stop the bleeding, uses small cells called platelets (PLATE-lets) that clump together at the location of injury to plug the hole in the blood vessel. VWF acts like glue to help the platelets stick together and to the blood vessel wall to stop the bleeding.
Inheritance
Normal vWF levels are greater than 0.50 IU/mL. This can sometimes be referred to as “50%” level. Some people may have lower levels of vWF but experience no bleeding. This is common in people who are blood group O as their vWF levels are naturally lower.
People who experience bleeding with mildly lowered vWF levels (0.30-0.50 IU/ mL) have a condition called “Low vWF”. While people with Low vWF are born with low levels, the inheritance pattern, how it is passed down from parent to child, is not well understood and other family members can be affected differently.
If your vWF level is less than (0.30 IU/mL (“30%”) you have a diagnosis of von Willebrand Disorder (vWD). In this case, it is almost always inherited (passed down) from a parent to a child. vWD can be passed down from either the mother or the father, or both, to their son or daughter (Fig 1).
The son or daughter of a parent with vWD has a 50% chance of having vWD. The “type” of the vWD, indicates how the condition is passed down. In type 1 and 2, if one parent has vWD and does pass it to their child, then that child will have the condition. In type 3, the child usually inherits the condition from both parents. Even if, both parents have vWD, the child could get either a mild or severe form of the vWD based on how the condition is passed on. People with vWD can have different experiences of bleeding, depending on their “type” and even within “types”, some people may experience bleeding more than others.
See the Von Willebrand Disorder Booklet here.
