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USMLE – von Willebrand’s Disease (vWD)

Pathophysiology
1. Type of bleeding disorder (can be inherited or acquired) due to a defect in, or reduction of von Willebrand factor
2. Four inherited forms exist – type I, type IIb, type IIN, and type III
3. Type I – most common, with mild to moderate symptoms; vWF is 50% decreased
4. Types IIb and IIN – amount of vWF is near normal but activity is decreased
5. Type III – defect in both amount and activity of vWF; a rare and severely hemorrhagic condition

Signs and Symptoms
1. Severity of symptoms is highly variable – from bleeding only after surgery or trauma to spontaneous
2. Epistaxis
3. Gastrointestinal bleeding
4. Genitourinary tract bleeding
5. Petechiae
6. Ecchymosis
7. Hemarthrosis

Characteristic Test Findings
1. Prolonged bleeding time
2. Decreased amount of plasma vWF
3. Decreased biologic activity of vWF as measured by risocetin cofactor assay
4. Decreased factor 8
5. Thrombocytopenia

Histology/Gross Pathology
vWF is a multivalent protein that can bind two or more platelets

Associated Conditions
Acquired von Willebrand’s disease occurs in multiple transfusions, autoimmune disorders (Waldenstrom’s macroglobulinemia), lymphoproliferative disorders (lymphoma), and Wilm’s tumor

Biochemistry
1. Inherited form – see pathophysiology
2. Acquired form – occurs when antibodies develop that absorb or inhibit vWF

Inheritance/Epidemiology
1. Most common type of inherited bleeding disorder
2. Types I, IIb, and IIN – autosomal dominant
3. Type III – autosomal recessive

Treatment
1. Inherited type I – factor 8 concentrate (contains vWF) every 12 hours for 2-3 days before and after surgical procedure
2. DDAVP (raises amount of vWF) can be given for maximum of 48 hours and requires pretesting to ensure efficacy
3. If menorrhagia occurs, use oral contraceptives to stop menses
4. Acquired disease – requires adequate treatment of underlying causes
5. Factor 8 concentrate and DDAVP don’t work

Tips for the USMLE
1. Main functions of vWF are to facilitate platelet adhesion and to carry the anti-hemophilic factor 8 intravascularly
2. Four most consistent lab findings – prolonged bleeding time, decreased amount of activity of vWF, and decreased amount of factor 8
3. Other lab findings (and to some degree the four listed above) can vary over time and are occasionally even normal
4. Factor 8 concentrate and DDAVP are both effective treatments; DDAVP is preferred by some patients to avoid risks associated with transfusion of blood factors
5. Factor 8 works in types I, IIb, and IIN
6. DDAVP works in only some cases of type I
7. If ristocetin co-factor assay is mentioned, think vWD

Lillian Thompson By Lillian Thompson

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