Von Willebrand disease causes
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VWD is caused by a quantitative or qualitative defect in vWF. Von Willebrand Factor binds platelets to collagen and is important in primary hemostasis. It also serves as a carrier for Factor VIII and prevents it form being degraded. Most cases of vWD are due to inherited mutations that affect production of vWF. There are also acquired forms of vWD where vWF is impaired due to another process.
There are three types of inherited vWD, caused by different defects in vWF:
- Type 1: Quantitative defect of vWF, but the protein functions properly. There is just less vWF than there should be. This is the most common form.
- Type 2: A group of quantitative defects in vWF. There are four subtypes
- Type 2A: Loss of just high molecular weight vWF multimers due to either defects in assembly or increased vulnerability to cleavage by vWF-protease. High weight multimers are the most active, so loss of these causes increased bleeding.
- Type 2B: Stronger than normal binding of vWF to platelets leads to loss of high weight multimers from circulation.
- Platelet type vWD (or pseudo-vWD) is caused by a gain-of-function mutation in the platelet receptor that also leads to stronger binding to vWF
- Type 2N: Loss of ability of vWF to bind to factor VIII. Behaves similar to a mild hemophilia A due to decreased factor VIII levels.
- Type 2M: vWF dysfunction due to defective binding to platelets
- Type 3: Complete absence of vWF.[1]
Acquired defects in vWF can also be due to a number of conditions including hematologic malignancies and aortic stenosis (Heyde syndrome).
References
- ↑ Favarolo et al. Von Willebrand Disease and Platelet Disorders. Hemophilia 2014; 20: 59-64.