Von Willebrand Disease

Dr. Arvind Kumar

Introduction

  • Von Willebrand disease (VWD) is one of the most common inherited bleeding disorders.
  • It occurs due to a deficiency or dysfunction of von Willebrand factor (VWF), a protein essential for normal blood clotting.
  • VWF plays two major roles in hemostasis:
    1. Helps platelets adhere to the injured blood vessel wall.
    2. Carries and stabilizes coagulation factor VIII in the bloodstream.
  • Deficiency or dysfunction of VWF can lead to prolonged or excessive bleeding.
  • The disease affects both males and females, although women may experience additional complications related to heavy menstrual bleeding, pregnancy, and childbirth.
  • The severity ranges from mild bleeding symptoms to severe bleeding complications.

Functions 

1. Platelet Adhesion

  • VWF binds to exposed collagen at the site of blood vessel injury.
  • It interacts with platelet glycoprotein Ib (GPIb).
  • This interaction helps platelets adhere to the damaged vessel wall.
  • It is an essential step in primary hemostasis.

2. Transport of Factor VIII

  • VWF binds to coagulation factor VIII in the circulation.
  • It protects factor VIII from premature degradation.
  • Reduced VWF levels may lead to decreased factor VIII activity.
  • This can impair secondary hemostasis.

Clinical significance: VWF deficiency primarily affects platelet adhesion, while reduced factor VIII activity may additionally impair the coagulation cascade.

Etiology and Risk Factors

1. Inherited Causes

  • Genetic mutations: Changes in the VWF gene affect the production, structure, or function of VWF.
  • Family history: The disorder may occur in multiple family members.
  • Autosomal dominant inheritance: Common in type 1 and many type 2 cases.
  • Autosomal recessive inheritance: Common in type 3 and certain type 2 variants.

2. Acquired Von Willebrand Syndrome

  • Acquired von Willebrand syndrome develops later in life and is not caused by an inherited VWF gene variant.

It may be associated with:

  • Certain cardiovascular disorders, including severe aortic stenosis.
  • Lymphoproliferative disorders.
  • Myeloproliferative disorders.
  • Autoimmune conditions.
  • Conditions that increase VWF clearance or interfere with its function.

Clinical note: Acquired von Willebrand syndrome should be considered when a patient develops new bleeding symptoms without a clear family history.

Classification 

Von Willebrand disease is classified into three major types.

1. Type 1: Partial Quantitative Deficiency

  • Characterized by a reduced concentration of VWF.
  • The protein generally retains its normal function.
  • It is the most common type of VWD.
  • Bleeding is usually mild to moderate.
  • VWF antigen and VWF activity are reduced.
  • Factor VIII activity may be mildly reduced.

2. Type 2: Qualitative Defect

  • Characterized by abnormal VWF function.
  • VWF concentration may be normal or reduced.
  • Platelet adhesion or factor VIII binding may be impaired.

Major subtypes:

Type 2A

  • Reduced platelet-dependent function.
  • Loss of high-molecular-weight VWF multimers.
  • Impaired platelet adhesion.

Type 2B

  • Increased affinity of VWF for platelet GPIb.
  • May cause thrombocytopenia.
  • Requires careful selection of treatment.

Type 2M

  • Reduced platelet-dependent VWF function.
  • High-molecular-weight multimers are generally preserved.

Type 2N

  • Reduced binding of VWF to factor VIII.
  • May cause markedly reduced factor VIII activity.
  • Can resemble hemophilia A.

3. Type 3: Severe Quantitative Deficiency

  • Characterized by a near-complete absence of VWF.
  • VWF antigen and activity are very low or undetectable.
  • Factor VIII activity may be markedly reduced.
  • Patients may experience severe mucosal bleeding.
  • Joint and muscle bleeding may occur because of reduced factor VIII activity.
Type Classification Defect Key Characteristics
Type 1 Partial quantitative deficiency Reduced VWF concentration Most common type; VWF function is generally preserved; bleeding is usually mild to moderate.
Type 2A Qualitative defect Reduced platelet-dependent activity with loss of high-molecular-weight VWF multimers Impaired platelet adhesion and abnormal VWF multimer distribution.
Type 2B Qualitative defect Increased affinity of VWF for platelet glycoprotein Ib (GPIb) May cause thrombocytopenia due to increased platelet binding.
Type 2M Qualitative defect Reduced platelet-dependent activity without characteristic loss of high-molecular-weight multimers Impaired platelet adhesion despite relatively preserved multimer distribution.
Type 2N Qualitative defect Reduced binding of VWF to factor VIII Reduced factor VIII levels; may resemble hemophilia A.
Type 3 Severe quantitative deficiency Near-complete absence of VWF Most severe form; markedly reduced factor VIII levels and increased risk of serious bleeding.

Clinical Features 

1. Mucocutaneous Bleeding

  • Frequent or prolonged nosebleeds.
  • Easy bruising after minor trauma.
  • Bleeding from the gums.
  • Prolonged bleeding from minor cuts.
  • Excessive bleeding after dental procedures.

2. Menstrual and Obstetric Bleeding

  • Heavy menstrual bleeding.
  • Prolonged menstrual periods.
  • Iron-deficiency anemia due to repeated blood loss.
  • Increased risk of postpartum hemorrhage.

3. Bleeding After Procedures

  • Excessive bleeding during or after surgery.
  • Prolonged bleeding following tooth extraction.
  • Increased bleeding after invasive procedures.

4. Severe Bleeding Manifestations

  • Gastrointestinal bleeding.
  • Muscle hematomas.
  • Joint bleeding, particularly in severe disease.
  • Significant blood loss requiring medical intervention.

Important: Clinical manifestations vary according to disease subtype and severity. Mild VWD may remain undiagnosed for years.

Laboratory Diagnosis

Laboratory investigations help confirm the diagnosis, determine disease severity, and distinguish VWD from other bleeding disorders.

1. Complete Blood Count (CBC)

  • Evaluates hemoglobin, hematocrit, red blood cell indices, and platelet count.
  • Hemoglobin may be reduced due to chronic blood loss.
  • Platelet count is usually normal.
  • Thrombocytopenia may occur in type 2B VWD.

2. Bleeding Assessment Tools

  • Used to document the patient’s bleeding history.
  • Evaluate nosebleeds, bruising, heavy menstrual bleeding, and bleeding after procedures.
  • Help determine whether specific laboratory investigations are indicated.
  • Cannot independently confirm or exclude VWD.

3. Von Willebrand Factor Antigen (VWF:Ag)

  • Measures the concentration of VWF in plasma.
  • Reduced levels suggest a quantitative deficiency.
  • May be reduced in type 1 and type 3 VWD.
  • Must be interpreted alongside VWF activity.

4. Von Willebrand Factor Activity

  • Evaluates the functional activity of VWF.
  • Modern assays include platelet-binding activity methods, such as GPIb-based assays.
  • Reduced activity may indicate impaired VWF function.
  • Comparison with VWF antigen helps distinguish quantitative deficiency from qualitative dysfunction.

5. Factor VIII Activity

  • Measures the activity of coagulation factor VIII.
  • Factor VIII may be normal or mildly reduced in type 1 VWD.
  • It may be markedly reduced in type 3 and type 2N VWD.
  • Helps evaluate the effect of VWF deficiency on secondary hemostasis.

6. Activated Partial Thromboplastin Time (aPTT)

  • Evaluates the intrinsic and common coagulation pathways.
  • May be normal in mild VWD.
  • May be prolonged when factor VIII activity is sufficiently reduced.
  • A normal aPTT does not exclude VWD.

7. Prothrombin Time (PT)

  • Evaluates the extrinsic and common coagulation pathways.
  • PT is generally normal in VWD.
  • It helps assess alternative causes of abnormal bleeding.

8. VWF Multimer Analysis

  • Evaluates the distribution of VWF multimers of different molecular sizes.
  • Helps identify abnormalities in VWF structure.
  • Supports differentiation of selected type 2 subtypes, particularly types 2A and 2B.

9. Genetic Testing

  • Identifies selected variants in the VWF gene.
  • May help clarify uncertain diagnoses.
  • Can support family counseling.
  • Is not required in every patient.

Laboratory note: Bleeding time is not recommended as a reliable test for diagnosing VWD.

Laboratory Findings in Von Willebrand Disease

Investigation Type 1 Type 2 Type 3
CBC Usually normal; anemia may occur Usually normal; thrombocytopenia may occur in type 2B Usually normal; anemia may occur
Platelet count Usually normal May be reduced in type 2B Usually normal
PT Usually normal Usually normal Usually normal
aPTT Normal or prolonged Normal or prolonged May be prolonged
VWF antigen Reduced Normal or reduced Very low or undetectable
VWF activity Reduced Often disproportionately reduced relative to antigen Very low or undetectable
Factor VIII activity Normal or reduced Variable; markedly reduced in type 2N Often markedly reduced
VWF multimers Usually preserved distribution Abnormal in some subtypes Absent or nearly absent

Note: These are typical findings. Results vary according to subtype, disease severity, and laboratory methods.

Differential Diagnosis

1. Hemophilia A

  • Caused by factor VIII deficiency.
  • Commonly produces deep-tissue bleeding, muscle hematomas, and joint bleeding.
  • Factor VIII activity is reduced.
  • VWF antigen and activity are generally normal.

2. Hemophilia B

  • Caused by factor IX deficiency.
  • May produce muscle bleeding, joint bleeding, and prolonged bleeding after injury.
  • Factor IX activity is reduced.

3. Platelet Function Disorders

  • Result from abnormalities in platelet adhesion, activation, or aggregation.
  • May produce symptoms similar to VWD.
  • Require appropriate platelet function investigations.

4. Immune Thrombocytopenia

  • Characterized by a reduced platelet count.
  • May cause petechiae, bruising, and mucosal bleeding.
  • Differentiation requires a CBC and appropriate clinical assessment.

5. Acquired Von Willebrand Syndrome

  • Develops in association with another medical condition.
  • Is not caused by an inherited VWF gene variant.
  • May resemble inherited VWD clinically and in laboratory investigations.

Treatment 

Treatment depends on the disease subtype, severity of bleeding, previous treatment response, and the clinical situation.

1. Desmopressin (DDAVP)

  • Stimulates the release of stored VWF and factor VIII from endothelial cells.
  • May be used in selected patients with type 1 VWD.
  • May be suitable for some type 2 variants following specialist assessment.
  • Is generally ineffective in type 3 VWD.
  • Is contraindicated in type 2B because it may worsen thrombocytopenia.
  • May require a response trial before therapeutic use.
  • Fluid restriction and sodium monitoring may be necessary because of the risk of hyponatremia.

2. Von Willebrand Factor Concentrates

  • Replace deficient or dysfunctional VWF.
  • May be required for severe bleeding.
  • Used when desmopressin is ineffective, contraindicated, or unsuitable.
  • May be required before major surgery.
  • Are important in the management of selected patients with type 3 VWD.

3. Antifibrinolytic Agents

  • Tranexamic acid helps stabilize blood clots by reducing fibrin breakdown.
  • May be used for mucosal bleeding.
  • May help control bleeding after dental procedures.
  • May be used for heavy menstrual bleeding in appropriate patients.

4. Hormonal Treatment

  • Combined hormonal contraceptives may help manage heavy menstrual bleeding.
  • Progestin-based treatments may be appropriate for selected patients.
  • Treatment should be individualized according to clinical needs.

5. Iron Supplementation

  • May be required when repeated bleeding causes iron deficiency.
  • Helps replenish iron stores.
  • Can improve iron-deficiency anemia associated with chronic blood loss.

6. Prevention of Bleeding

  • Inform healthcare professionals about the diagnosis before surgery or dental procedures.
  • Avoid unnecessary use of aspirin and other medications that impair platelet function unless specifically indicated by a clinician.
  • Follow an individualized bleeding-management plan.
  • Seek specialist advice before invasive procedures.
  • Obtain appropriate medical care for significant or persistent bleeding.

Complications 

  • Iron-deficiency anemia: May result from repeated blood loss.
  • Heavy menstrual bleeding: Can interfere with daily activities and reduce quality of life.
  • Postpartum hemorrhage: May occur after childbirth.
  • Postoperative bleeding: Can complicate surgical recovery.
  • Gastrointestinal bleeding: May cause recurrent blood loss.
  • Joint and muscle bleeding: More likely in severe disease.
  • Treatment-related complications: Desmopressin may cause hyponatremia in susceptible patients.

Early diagnosis and appropriate treatment can reduce the risk of complications.

Prevention and Genetic Counseling

Although inherited VWD cannot generally be prevented, bleeding complications can often be minimized.

  • Obtain a detailed personal and family bleeding history.
  • Investigate unexplained recurrent bleeding.
  • Inform healthcare professionals about the condition before surgery, dental treatment, and childbirth.
  • Consider genetic counseling in families affected by severe VWD.
  • Develop individualized bleeding-management plans.
  • Arrange appropriate follow-up with a hematologist when indicated.

Clinical Significance 

  • Diagnosis of bleeding disorders: VWD should be considered in patients with recurrent mucocutaneous bleeding.
  • Evaluation of heavy menstrual bleeding: It is an important potential cause of excessive menstrual blood loss.
  • Investigation of unexplained bleeding: It may explain prolonged bleeding after dental procedures, surgery, or minor injuries.
  • Interpretation of coagulation tests: Normal PT and aPTT do not exclude VWD.
  • Preoperative assessment: Diagnosis helps guide preventive measures before invasive procedures.
  • Pregnancy management: Identification of VWD helps clinicians plan delivery and reduce bleeding complications.
  • Differential diagnosis: It must be distinguished from hemophilia and platelet function disorders.
  • Genetic counseling: Family assessment may help identify affected relatives.
  • Prevention of complications: Early diagnosis can reduce the risk of severe bleeding and iron-deficiency anemia.
  • Individualized treatment: Identification of the disease subtype helps guide treatment selection.