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Von Willebrand Disease

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

The symptoms of von Willebrand disease may include:

• bruising that's unusual in location or frequency
• abnormal menstrual bleeding
• bleeding in the mucous membranes, such as the gums, nose, and lining of the gastrointestinal system
• excessive or prolonged bleeding after a tooth is pulled or tonsils are removed or prolonged oozing from cuts

Diagnosis

• Normal platelet count
• Prolonged bleeding time
• Reduced von Willebrand factor level
• Reduced platelet aggregation ( platelet aggregation test )
• Ristocetin co-factor is reduced

This disease may also alter the results of the following tests:

• Factor VIII level
• Von Willebrand factor multimers

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, 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.