Von Willebrand's disease
Von Willebrand's disease: Excerpt from Handbook of Diseases
A hereditary bleeding disorder, von Willebrand’s disease is characterized by prolonged bleeding time, moderate deficiency of clotting Factor VIIIAHF (antihemophilic factor), 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. Prognosis, however, is usually good.
Causes
Unlike hemophilia, von Willebrand’s disease is inherited as an autosomal dominant trait and occurs more often in females. 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 von Willebrand factor (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.
Signs and symptoms
Von Willebrand’s disease produces easy bruising, epistaxis, and bleeding from the gums. 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 rarely occur. The severity of bleeding may lessen with age. Bleeding episodes typically occur sporadically — a patient may bleed excessively after one dental extraction but not after another.
Diagnosis
Diagnosing this disease 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 diagnosis. Typical laboratory data include:
❑ prolonged bleeding time (> 6 minutes)
❑ slightly prolonged partial thromboplastin time (> 45 seconds)
❑ absent or reduced levels of Factor VIII-related antigens (VIIIAHN), 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 aims 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, intravenous 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 by enhancing cellular release of stored Factor VIII.
Special considerations
❑ Care 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 seek medical attention after even minor trauma and before all surgery, to determine whether replacement of blood components is necessary.
❑ Tell the patient to watch for signs of hepatitis for 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 of von Willebrand’s disease to avoid contact sports.
❑ Encourage the patient to wear a medical identification bracelet at all times.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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» Next page: Consider von Willebrand Disease (vWD) in teenage patients with menorrhagia during menarche (Avoiding Common Pediatric Errors)
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