How is von Willebrand Disorder inherited?
Von Willebrand disorder is mostly a genetic disorder. This means it is passed down through the genes from parent to child. The altered gene in von Willebrand disorder is on one of the regular chromosomes, not on one of the sex chromosomes (like haemophilia). This means that, unlike haemophilia which affects more males, von Willebrand disorder affects males and females in equal numbers.
There are two main inheritance patterns for VWD:
In most type 1 and type 2A, 2B and 2M VWD, the VWD gene is dominant. This means that if one parent has a VWD gene, they have a one in two (50%) chance of passing the gene on to each of their children. They or their children may or may not have symptoms.
In type 3 and type 2N and some type 1 and 2A VWD, the VWD gene is recessive. If both parents carry this type of VWD, they may not have symptoms but there is a one in four (25%) chance that their children could inherit a copy of the VWD gene from both of them and have symptoms, usually severe. There is a one in two (50%) chance that their children will inherit only one copy of the VWD gene from them and carry the gene but not have symptoms, like their parents. There is also a one in four (25%) chance that their children will not inherit the VWD gene at all.
If one member of a family is diagnosed with VWD, the doctor may recommend testing other members to see whether they have VWD as well.