Von Willebrand's disease (vWD) results from the deficiency or abnormal function of von Willebrand factor (vWF). vWF is a multimeric glycoprotein encoded for by gene map locus 12p13. It is made in the endothelium and stored in Weibel-Palade bodies. It has two main functions:
- It assists in platelet plug formation by attracting circulating platelets to the site of damage.
- It binds to coagulation factor VIII preventing its clearance from the plasma.
- Prevalence is as high as 1-2% in the general population on unselected screening.
- Worldwide incidence is around 125 per million with between 0.5 and 5 per million being severely affected.
- Most patients have mild disease.
- It is more common in females.
- It is more severe with blood type O.
This varies according to the extent of the deficiency:
- Bleeding tendency from mucosa - eg, epistaxis, menorrhagia (consider in women with no other obvious cause).
- Spontaneous bleeding - eg, internal or joint bleeding (only in the most severe of cases).
- Blood clots during childbirth (rare).
- Death may occur.
- Hereditary - three types (see below).
- Acquired - also called pseudo-von Willebrand's disease or platelet-type; it is frequently found in lymphoproliferative or myeloproliferative disorders, and can also be associated with solid tumours, immunological and cardiovascular disorders, and various other conditions - eg, aortic stenosis, Wilms' tumour, hypothyroidism.
Classification of hereditary types
Types of hereditary von Willebrand's disease (vWD)
Type of vWD
Epidemiology - percentage of all cases
Quantitative or qualitative defect
|60-80%||Quantitative defect (19-45% of enzyme level present)||
|20-30%||Qualitative defect - multimers abnormal or subgroups absent||
|Rare - the most severe form; 1-5% of cases||Quantitative - levels very low or undetectable||
|Rare - fewer than 70 cases described||Functional mutations of vWF receptor on platelet||
Subtypes of type 2
- Abnormal synthesis or proteolysis of vWF multimers.
- Leads to small multimers in circulation; factor VIII still binds as normal.
- Spontaneous binding of platelets with rapid clearance of platelets and large vWF multimers.
- Mild thrombocytopenia.
- Factor VIII binding normal or low normal.
- Desmopressin will not help, as it leads to unwanted platelet aggregation.
- Low or absent binding to receptor on platelets.
- Factor VIII binds as normal.
- Autosomal recessive rather than X-linked.
- Shows incomplete response to haemophilia A treatment.
- Factor VIII levels reduced to around 5%, as vWF has a reduced affinity for factor VIII.
See also separate article Bleeding Disorders.
The severity of vWD varies and many patients will never be diagnosed, as their disorder may never come to light. In practice - both primary and secondary - the patients with more severe forms of the disorder will present with abnormal bleeding.
Following this, basic blood tests including FBC, clotting screen and liver function should be performed and patients should be referred for a specialist opinion and other more specialised investigations such as plasma levels of vWf. The haematologist will also be able to test for other bleeding disorders which will form part of the differential diagnosis.
- Bloods including FBC, fibrinogen level, platelet count, clotting screen, factor IX levels. The platelet count and morphology are normal.
- Plasma levels of vWF - keep in mind that deficiency can be quantitative or qualitative.
- Quantitative deficiency - detected by vWF antigen assay.
- Qualitative deficiency - detected by a number of methods including glycoprotein binding assay, ristocetin cofactor activity, ristocetin-induced platelet agglutination.
- Factor VIII measurement:
- Factor VIII binds to vWF which in turn prevents the rapid breakdown of factor VIII; thus, a deficiency of vWF can also lead to deficiency of factor VIII.
- In type 2 vWF - factor VIII levels are normal; studies of platelet aggregation with sub-endothelium are necessary.
- Oestrogens, vasopressin and growth hormone all elevate levels.
Pregnancy and von Willebrand's disease
During pregnancy the level of vWF increases in most women with types 1 and 2 vWD and labour and delivery usually proceed normally. However, patients with type 2B disease may experience haemorrhagic problems.
- Educate patients as to the bleeding risk. Provide advice regarding drugs that must be avoided such as non-steroidal anti-inflammatory drugs and antiplatelet drugs.
- Minor bleeding problems, such as bruising or a brief nosebleed, may not require any specific treatment.
- The two main treatment options are desmopressin (DDAVP®) and transfusion therapy. Platelet transfusions may be helpful in some patients with disease refractory to other therapies.
- DDAVP® can be used to treat bleeding complications or to prepare patients for surgery.
- For prophylaxis in major surgery or for treatment of serious bleeding episodes, vWF-containing factor VIII concentrates are the treatment of choice. However, there have been a few reported cases of venous thromboembolic complications in surgical vWD patients prophylactically treated with factor VIII concentrates.
- DDAVP® is first-line in type I vWD; in all other types, factor VIII-vWF concentrates are first-line. If the response to the first-line agents is poor, then the other can be tried as an alternative (not in type 3).
- In type 2B, DDAVP® may cause a paradoxical drop in the platelet count and should not be used without prior testing to see how the patient responds.
- DDAVP® is ineffective in type 3 as there are no vWF levels to boost.
- Antifibrinolytics (aminocaproic acid, tranexamic acid) may be used, especially in combination with other medications for dental extractions and oral surgery.
- Patients who have alloantibodies to vWF will require recombinant factor VIII.
Further reading & references
- Von Willebrand's disease, The Haemophilia Society
- Von Willebrand Disease, Type 1, VWD1; Online Mendelian Inheritance in Man (OMIM)
- Federici AB; Acquired von Willebrand syndrome: an underdiagnosed and misdiagnosed bleeding complication in patients with lymphoproliferative and myeloproliferative disorders. Semin Hematol. 2006 Jan;43(1 Suppl 1):S48-58.
- Guidelines for the laboratory investigation of heritable disorders of platelet function, British Committee for Standards in Haematology, 2011
- Chalmers EA; Neonatal coagulation problems. Arch Dis Child Fetal Neonatal Ed. 2004 Nov;89(6):F475-8.
- Pollack ES; von Willebrand Disease. Medscape, Apr 2012
- Geil JD; Pediatric Von Willebrand Disease, Medscape, Apr 2012
- Mannucci PM; Treatment of von Willebrand's Disease. N Engl J Med. 2004 Aug 12;351(7):683-94.
|Original Author: Dr Gurvinder Rull||Current Version: Dr Colin Tidy||Peer Reviewer: Dr Hannah Gronow|
|Last Checked: 28/02/2013||Document ID: 2928 Version: 22||© EMIS|
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