Von Willebrand's Disease for PA
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Overview of von Willebrand’s Disease (vWD) for the Physician Assistant Licensing Exam
- Definition:
- Von Willebrand’s disease (vWD) is the most common inherited bleeding disorder, due to a quantitative or qualitative defect in von Willebrand factor (vWF).
- vWF is essential for platelet adhesion at injury sites and stabilizes factor VIII, an important clotting factor.
- Types of vWD:
- Type 1: Most common form, with a partial quantitative deficiency of vWF. Patients often have mild symptoms like bruising or bleeding with injury or surgery.
- Type 2: Qualitative defect in vWF function, with several subtypes:
- 2A: Reduced high-molecular-weight multimers, impairing platelet adhesion.
- 2B: Increased binding to platelets, causing platelet clearance.
- 2M: Defective binding to platelets with normal multimer pattern.
- 2N: Reduced binding to factor VIII, resembling hemophilia A.
- Type 3: Severe deficiency or absence of vWF, leading to symptoms similar to hemophilia, including joint and muscle bleeds.
Clinical Presentation
- Symptoms:
- Mucocutaneous Bleeding: Epistaxis, easy bruising, gingival bleeding, and menorrhagia are common, especially in types 1 and 2.
- Prolonged Bleeding: After surgery or dental procedures.
- Severe Bleeding (Type 3): May include hemarthrosis and deep tissue bleeding.
- Family History: Often positive in types 1 and 2 due to autosomal dominant inheritance.
Diagnosis
- Initial Tests:
- CBC: Usually normal, though anemia may be seen with chronic bleeding.
- PT: Normal.
- aPTT: May be prolonged due to factor VIII deficiency.
- Specialized Tests:
- vWF Antigen: Measures vWF levels; low in types 1 and 3.
- Ristocetin Cofactor Activity: Assesses vWF function by testing its ability to bind platelets; low in types 1, 2A, 2B, and 3.
- Factor VIII Activity: Often low in severe cases.
Treatment
- Desmopressin (DDAVP):
- Effective in mild type 1 and some type 2 cases by releasing vWF from endothelial stores.
- Not effective for type 3 or type 2B.
- vWF-Containing Factor VIII Concentrates:
- Used for patients unresponsive to DDAVP, particularly in type 3 or severe cases.
- Antifibrinolytics:
- Tranexamic acid or aminocaproic acid as adjunctive therapy for mucosal bleeding.
- Hormonal Therapy: Used for menorrhagia, including oral contraceptives or levonorgestrel-releasing IUDs.
Key Points
- vWD is the most common inherited bleeding disorder and can be classified into types 1, 2, and 3, with varying severity.
- Type 1 involves mild deficiency of vWF, while type 3 involves a near-complete absence, leading to severe bleeding.
- Diagnosis includes CBC, vWF antigen, ristocetin cofactor activity, and factor VIII levels.
- Treatment includes DDAVP for mild cases, vWF-containing concentrates for severe cases, and antifibrinolytics for mucosal bleeding.