Von Willebrand's disease
Von Willebrand's disease: Excerpt from Professional Guide to Diseases (Eighth Edition)
Von Willebrand’s disease is a hereditary bleeding disorder characterized by prolonged bleeding time; moderate deficiency of von Willebrand’s factor (vWF), clotting factor VIII (antihemophilic factor) and, possibly, factor VIII coagulant protein (VIII:C); and impaired platelet function. This disease commonly causes bleeding from the skin or mucosal surfaces and, in females, excessive uterine bleeding. Bleeding may range from mild and asymptomatic to severe, potentially fatal hemorrhage. The prognosis, however, is usually good.
Causes and incidence
Unlike hemophilia, von Willebrand’s disease is inherited as an autosomal dominant trait that affects males and females equally. One theory of pathophysiology holds that mild to moderate deficiency of factor VIII and defective platelet adhesion prolong coagulation time. Specifically, this results from a deficiency of the vWF, which stabilizes the factor VIII molecule and is needed for proper platelet function.
Defective platelet function is characterized by:
❑ decreased agglutination and adhesion at the bleeding site
❑ reduced platelet retention when filtered through a column of packed glass beads
❑ diminished ristocetin-induced platelet aggregation.
Recently, an acquired form has been identified in patients with cancer and immune disorders.
Von Willebrand’s disease, which doesn’t have any racial or ethnic associations, affects about 1% of the population.
Signs and symptoms
Von Willebrand’s disease produces easy bruising, epistaxis, and bleeding from the gums. Petechiae are rarely seen. Severe forms of this disease may cause hemorrhage after laceration or surgery, menorrhagia, and GI bleeding. Excessive postpartum bleeding is uncommon because factor VIII levels and bleeding time abnormalities become less pronounced during pregnancy. Massive soft-tissue hemorrhage and bleeding into joints seldom occur. Severity of bleeding may lessen with age, and bleeding episodes occur sporadically — a patient may bleed excessively after one dental extraction but not after another.
Diagnosis
Diagnosis is difficult because symptoms are mild, laboratory values are borderline, and factor VIII levels fluctuate. However, a positive family history and characteristic bleeding patterns and laboratory values help establish the diagnosis. Typical laboratory data include:
❑ prolonged bleeding time (more than 6 minutes)
❑ slightly prolonged partial thromboplastin time (more than 45 seconds)
❑ absent or reduced levels of factor VIII-related antigens and low factor VIII activity level
❑ defective in vitro platelet aggregation (using the ristocetin coagulation factor assay test)
❑ normal platelet count and normal clot retraction.
Treatment
The goals of treatment are to shorten bleeding time by local measures and to replace factor VIII (and, consequently, vWF) by infusion of cryoprecipitate or blood fractions that are rich in factor VIII.
During bleeding and before surgery, I.V. infusion of cryoprecipitate or fresh frozen plasma (in quantities sufficient to raise factor VIII levels to 50% of normal) shortens bleeding time. Desmopressin given parenterally or intranasally is effective in raising serum levels of vWF.
Special considerations
The care plan should include local measures to control bleeding and patient teaching to prevent bleeding, unnecessary trauma, and complications.
❑ After surgery, monitor bleeding time for 24 to 48 hours, and watch for signs of new bleeding.
❑ During a bleeding episode, elevate and apply cold compresses and gentle pressure to the bleeding site.
❑ Refer parents of affected children for genetic counseling.
❑ Advise the patient to consult the physician after even minor trauma and before all surgery to determine if replacement of blood components is necessary.
❑ Instruct the patient to watch for signs of hepatitis within 6 weeks to 6 months after transfusion.
❑ Warn the patient against using aspirin and other drugs that impair platelet function.
❑ Advise the patient who has a severe form to avoid contact sports.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Von Willebrand's disease (Handbook of Diseases)
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