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Definition and Epidemiology of von Willebrand Disease
Increased bleeding tendency: von Willebrand disease
The von Willebrand disease is named after the Finnish physician Erik von Willebrand. He examined a family living on the Aaland islands in the Baltic sea that suffered from severe bleeding. He jokingly called the island “Nose Bleed Island”.
He summarised the conclusions of his examination, creating a new clinical picture and calling it “pseudohaemophilia”, separating it from the clinical picture of a haemophilia. By and by this clinical picture became known as “von Willebrand disease”.
The von Willebrand disease (vWD) is the most common inherited disorder of hemostasis with a relatively high prevalence (1 : 100). Men and women are equally affected. The disease is caused by qualitative or quantitative deficiency of von Willebrand factor with various forms of clinical manifestation. In order to understand the concept of this hemorrhagic diathesis you should get to know the function of von Willebrand factor better.
Pathophysiology of von Willebrand Disease
The von Willebrand factor (vWF) is a glycoprotein that is produced in endothelium and megacaryocytes and is then located in the so-called Weibel-Palade-bodies as a multimer. It is involved in various processes of hemostasis:
- During primary hemostasis the vWR binds to proteins of the subendothelial matrix and the surface of platelets. This generates a adhesive connection between endothelium and platelets. Glycoprotein Ib/IX on the surface of platelets plays an important role in here.
- As a result of the adhesion to the platelets the vWF activates platelet functions that result in platelet aggregation.
- The vWF forms a complex with clotting factor VIII in order to prevent its proteolytic degradation. This extends factor VIII’s half-time greatly and preserves its functions.
- The vWF is also an acute-phase protein that is synthesised and secreted increasingly in the course of inflammatory processes. It forms spontaneously into multimers in the plasma. Those multimers are proteolytic degraded by the protease ADAMTS13 that plays an important role in thrombotic microangiopathy and the hemolytic-uremic syndrome among others.
Etiology of von Willebrand Disease
Classification of the von Willebrand disease
Many forms of vWD are hereditary:
- The type 1 vWD (80 % of all cases) follows an autosomal dominant inheritance pattern and shows as a decrease level of vWD at 25 – 50 % of normal .
- The type 2 vWD is above all a qualitative defect. It causes various abnormal multimer structures. This results in an impaired function of vWF. There are different subtypes that come along with various manifestations in the clinical picture.
- The type 3 vWD (< 1 % of all cases ) is the most severe form that is caused by the complete absence of vWF factor. The inheritance pattern is autosomal recessive and the patient is severely affected.
Aside from this there are many forms of vWD that result from other underlying diseases. You can keep in mind that particularly hemato-oncological diseases, that come along with increased antibody production, can cause a vWD. This means specifically monoclonal gammopathies, malignant lymphomas and autoimmune or myeloproliferative diseases.
Von Willebrand disease and aortic valve stenosis
A rare but interesting phenomenon is the frequent coincidence of a symptomatic vDW in the course of an aortic valve stenosis. This coincidence is called Heyde’s syndrom and is not fully unterstood yet. It is assumed that in the plasma vWF forms multimeric clews like described above. This formation impedes the proteolytic degradation by ADAMTS13.
When the multimer flows through the stenotic aortic valve the resulting mechanical stress forces it to unroll. ADAMTS13 can now perform increased proteolytic degradation and reduces thus the vWF’s function. The vWF multimer is inactive when degraded and hence not able to perform it’s actual function in peripheral, defective blood vessels. The result is a vWS.
Clinical Picture of von Willebrand Disease
Symptoms of von Willebrand disease
Though the function of vWF is very complex and integrated in various processes, most of the patients don’t complain about symtomps at all or are affected by mild symptoms only.
The clinical picture depens like described above on the particular disease type. Thrombocytic and hemophilic bleeding types are predominant when there occurs pathological bleeding (pursuant to the pathophysiology). Mucosal bleeding is typically reported. Often the increased bleeding tendency doesn’t catch attention until increased peri- or postoperative after-bleeding occurs.
Diagnosis of von Willebrand Disease
Genetic diagnostics of von Willebrand disease
Due to the mostly genetic cause a detailed family medical history has to be done. Though in mild forms the vWD often remains undetected. The clinical bleeding type can lead to the answer to where in the hemostaseologic system this particular pathology is to be placed. The laboratory chemistry shows a prolonged bleeding time, possibly a prolongation of APPT and a deficiency of factor VIII. A vWD can however not be ruled out when the APPT and F VIII levels are normal.
A special von Willebrand diagnostic is indicated when there is a reasonable suspicion. It consists in the analysis of the present subtype via multimer analysis, vWF analysis and genetic diagnostics.
Treatment of von Willebrand Disease
Therapeutic options of von Willebrand disease
Patients should, like in all cases of hemorrhagic diathesis, perform an everyday prophylaxis. If there occurs bleeding or if an operation is necessary, it is essential to stop the bleeding accurately. Contraindicated are however ASA and other antiplatelet drugs.
There are several options for pharmaceutic treatment:
Minor bleeding can be treated with desmopressin (= analogue to ADH, DDAVP). It binds to V2 receptors and stimulates the release of von Willebrand factor from the Weibel-Palade-bodies. The effect of this release begins to work within 30 to 60 minutes and continues for several hours, so that a bleeding can be stopped. The release however depletes by and by, so the administration is limited. Application of desmopressin is possible as nasal spray or as pill. The nasal spray is a especially good everyday option for affected children.
- If there occurs Heavy bleeding, in particular peri- or postoperative one, the patient has to be substituted. It is also possible to use calculated substitutions when a certain bleeding is expected before. Here are usually given concentrates that contain factor VIII and vWF.
- Affected women can take oral contraceptives in order to weaken their menstrual bleeding and thus prevent larger loss of blood.
1. The von Willebrand disease…
- …shows always in form of petechiae.
- …shows always in form of sugillations.
- …shows always in form of a purpura.
- …can often take an asymptomatic course.
- …does always take an asymptomatic course.
2. You suspect a von Willebrand disease in a young female patient. What leads you to this suspicion?
- You see teleangiectasis in the mucosa of her nose.
- Laboratory chemistry shows a prolongation of bleeding time.
- Laboratory chemistry shows a prolongation of prothrombin time.
- Laboratory chemistry shows a shortening of prothrombin time.
- Laboratory chemistry shows a decrease in factor IX levels.
3. You want to figure out the cause of your patient’s von Willebrand disease. Which statement isn’t true?
- It is not necessary to do a family medical history.
- A secondary genesis due to an underlying disease is at her young age not worth considering.
- You apply the desmopressin test.
- The cause is always a qualitative defect in von Willebrand factor.
- The most common hereditary type follows an autosomal dominant inheritance pattern.