Chapter 29: Vascular-Venous and Lymphatic Disease
A 45-year-old woman presents for a preoperative evaluation. She relates a history of heavy bleeding during her menstrual cycles as well as easy bruising and bleeding gums. Bleeding time is 14 minutes. Which of the following is true?
(A) The disease is X-linked recessive.
(B) The most common variant is characterized by a functional abnormality.
(C) Ristocetin cofactor assay will be normal.
(D) Desmopressin is first-line treatment.
(E) Epistaxis occurs in 90% of affected patients.
(D) von Willebrand factor (vWF) is produced by endothelial cells and megakaryocytes and is a necessary cofactor for platelet binding to vessel walls. This patient has von Willebrand disease (vWD), an autosomal dominant disorder of coagulation resulting from deficiency or defect in vWF. vWD is the most common inherited coagulopathy. The majority (75–80%) of patients with vWD have type 1, a quantitative deficiency of vWF characterized by reduced factor VIII activity, vWF antigen, and ristocetin cofactor activity. Patients with type 1 vWD usually have mild or moderate platelet-type bleeding. Type 2 vWD is heterogeneous and further divided into four subtypes (2A, 2B, 2M, and 2N); the common feature is a qualitative defect in the vWF molecule. Patients with type 2 vWD usually have moderate to severe bleeding that presents in childhood or adolescence.
The initial laboratory evaluation of patients suspected by history of having vWD includes the following tests: assay of factor VIII activity, vWF antigen, and vWF ristocetin cofactor (Table 29-1). Platelet counts are usually normal, because this is a qualitative rather than a quantitative platelet disorder. Bleeding times will be prolonged (>11 minutes) secondary to a defect in platelet function. Because vWF with factor VIII binds together to form a complex, factor VIII levels in vWD patients are generally coordinately decreased along with plasma vWF, thus altering the activated partial thromboplastin time (aPTT) as well.
Table 29-1 Laboratory Diagnosis of von Willebrand Disease
|Type ||vWF Activity ||vWF Antigen ||Factor VIII ||RIPA ||Multimer Analysis |
|1 || ||↓ ||↓ ||Nl or ↓ ||↓ ||Normal pattern; uniform ↓ intensity of bands |
|2 ||A ||↓↓ ||↓ ||↓ ||↓ ||Large and intermediate multimers decreased or absent |
| ||B ||↓↓ ||↓ ||↓ ||↑ ||Large multimers decreased or absent |
|M ||↓ ||↓ ||↓ ||↓ ||Normal pattern; uniform ↓ intensity of bands |
|N ||Nl ||Nl ||↓↓ ||Nl ||Nl |
|3 || ||↓↓↓ ||↓↓↓ ||↓↓↓ ||↓↓↓ ||Multimers absent |
The ristocetin-induced platelet aggregation (RIPA) assay measures platelet agglutination caused by ristocetin-mediated vWF binding to platelet membrane glycoprotein GPIbα.
First-line treatment is desmopressin, an analogue of ...