What is von Willebrand Disease?

von Willebrand Disease (vWD) is a genetic disorder in which the blood does not clot properly. It is caused by a deficient or defective blood protein, von Willebrand factor. vWD is believed to be the most common bleeding disorder. It is estimated to affect up to 1% of the US population. Of the main subtypes, type I (the mildest form) is most common, accounting for 70% of all cases. Unlike hemophilia, the vWD gene is not on the sex chromosome, so occurs in men and women equally. Women are especially affected by von Willebrand disease during their menstrual period.

Symptoms include:

• Frequent nosebleeds
• Easy bruising
• Excessive bleeding following surgery or dental work
• Heavy or abnormal bleeding during menstrual periods
• Excessive bleeding after childbirth

Levels of Severity of vWD

There are three main types of vWD based on qualitative or quantitative defects in von Willebrand Factor (vWF). A fourth type, acquired vWD, is not hereditary.

Type 1 vWD is found in 60%-80% of patients.
This is the most common type, and the symptoms are usually mild. The amount of vWF levels in the blood are lower, ranging from 20%-50% of normal.

Type 2 vWD is found in 15%-30% of patients.
Symptoms are mild to moderate. The quality of the vWF is deficient in this type. Type 2 vWD is broken down to four subtypes, type 2A, type 2B, type 2M and type 2N.

Type 3 vWD is found in 5%-10% of patients.
This type of vWD is least common. The symptoms are typically severe, and include spontaneous bleeding episodes, often into joints and muscles.

People with type 3 vWD have almost a complete absence of vWF.

Acquired vWD

This type of vWD in adults results after a diagnosis of an autoimmune disease, such as lupus, or from heart disease or some types of cancer. It can also occur after taking certain medications.

Genetics of vWD

Von Willebrand disease can have different inheritance patterns. Most cases of type 1 and type 2 von Willebrand disease show an autosomal dominant inheritance pattern, which means one copy of the altered dominant gene from mom or dad is sufficient to cause the disorder.

If only one parent has a dominant inheritance type of vWD, with each pregnancy there is:

• A 50% chance of having a child (boy or girl) who inherits the vWD mutation
• A 50% chance of having a child (boy or girl) who does not inherit the vWD mutation

Type 3, some cases of type 2, and a small number of type 1 cases of von Willebrand disease are due to a autosomal recessive inheritance, which means both parents have passed on a copy of the mutated gene. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they do not show signs and symptoms of the condition.

If both parents carry a defective recessive gene for vWD, with each pregnancy there is:

• A 25% (one in four) chance of having a child who is unaffected
• A 25% (one in four) chance of having a child who has vWD
• A 50% chance of having a child who does not have vWD but carries the defective gene.

Type 2 vWD has subtypes (2A, 2B, 2M, and 2N) with qualitative defects and the inheritance patterns are more complicated and unique to each subtype. To inherit most cases of Types 2A, 2B and 2M vWD, the child needs only to inherit one defective gene from one parent to have the disorder and show symtoms. To inherit type 2N vWD, the child usually needs to inherit a defective vWF gene from each parent to show symptoms. For further information, please ask your Hemophilia Treatment Center nurse.

Source: www.nhf.org