Type 2 VWD

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Learning objectives

After completing this quiz, the learner should be able to:

  • interpret type 2 VWD as a group of qualitative VWF defects rather than a single disorder
  • distinguish type 2A, 2B, 2M, and 2N using functional laboratory patterns
  • apply the activity-to-antigen ratio without overextending it to type 2N
  • recognize why multimer analysis, RIPA, collagen-binding assays, and FVIII-binding assays answer different diagnostic questions
  • identify common pitfalls in distinguishing type 2A from type 2M and type 2B from platelet-type VWD
  • connect subtype classification to treatment implications, including desmopressin cautions
  • use subtype-specific reasoning to explain why antigen level alone does not predict bleeding risk

A patient has mucocutaneous bleeding, VWF 58 IU/dL, platelet-dependent VWF activity 22 IU/dL, FVIII 65 IU/dL, and reduced high-molecular-weight multimers. Which interpretation best fits this pattern?

a
Type 1 VWD
Type 1 VWD is a quantitative deficiency in which antigen and activity usually decrease proportionally, and high-molecular-weight multimers are generally preserved.
b
Type 2A VWD
The combination of disproportionately reduced platelet-dependent activity, a low activity-to-antigen ratio, and loss of high-molecular-weight multimers is characteristic of type 2A VWD. The defining problem is loss of the most hemostatically effective multimers, resulting in impaired platelet adhesion.
c
Type 2N VWD
Type 2N VWD primarily affects FVIII binding. Platelet-dependent activity and multimer distribution are usually relatively preserved.
d
Type 3 VWD
Type 3 VWD is characterized by virtual absence of VWF rather than a selective qualitative defect.

Which statement best captures the central diagnostic lesson of type 2 VWD?

a
VWF antigen is the most important test because type 2 VWD is always quantitative.
VWF antigen measures quantity, not function, and cannot diagnose qualitative defects by itself.
b
Type 2 VWD is defined by absent VWF.
Absent or nearly absent VWF defines type 3 VWD rather than type 2.
c
VWF may be present, but one of its functions is disproportionately impaired.
Type 2 VWD is a disorder of function rather than quantity. The protein may be present in normal or near-normal amounts, but one of its essential functions—platelet binding, collagen binding, multimer architecture, regulated platelet interaction, or FVIII binding—is impaired.
d
Type 2 VWD can be excluded if FVIII is normal.
FVIII may be normal in several type 2 subtypes, including many patients with type 2A, type 2B, and type 2M.

The platelet-dependent VWF activity-to-antigen ratio is most useful for identifying which type 2 patterns?

a
Type 2A, type 2B, and type 2M
A reduced activity-to-antigen ratio suggests qualitative VWF dysfunction and is especially useful for recognizing type 2A, type 2B, and type 2M. In these disorders, VWF function is impaired disproportionately relative to the amount of protein present.
b
Type 2N only
Type 2N usually preserves platelet-dependent VWF activity. The more informative clue is FVIII that is disproportionately low relative to VWF.
c
Type 3 only
Type 3 VWD is characterized by virtual absence of VWF rather than a disproportion between activity and antigen.
d
Acquired VWD only
Although acquired VWD can produce abnormal ratios, the activity-to-antigen ratio is not specific for acquired disease.

Which laboratory relationship is the key clue to type 2N VWD?

a
FVIII disproportionately low relative to VWF antigen
The key clue is FVIII that is too low for the amount of VWF antigen present. The abnormal relationship is between FVIII and VWF.
b
VWF antigen higher than platelet count
Platelet count does not define type 2N VWD.
c
PT disproportionately prolonged relative to aPTT
Type 2N may prolong the aPTT if FVIII is low enough, but PT is not the key diagnostic relationship.
d
VWF activity higher than VWF antigen
The central issue is impaired FVIII carriage, not VWF activity exceeding antigen.

A patient has low platelet-dependent VWF activity, a reduced activity-to-antigen ratio, and preserved high-molecular-weight multimers. Which diagnosis should be considered?

a
Type 2A VWD
Type 2A VWD typically shows loss of high-molecular-weight multimers.
b
Type 2M VWD
This pattern points toward type 2M VWD. The multimers are preserved, but platelet or collagen binding is impaired, producing reduced function despite intact multimer architecture.
c
Type 3 VWD
Type 3 VWD is characterized by absent or nearly absent VWF rather than preserved multimers.
d
Hemophilia B
Hemophilia B is a factor IX deficiency and does not produce abnormalities in VWF antigen, VWF activity, or multimer distribution.

Which finding most strongly suggests type 2B VWD or platelet-type VWD?

a
Normal PT
PT is usually normal in VWD and does not distinguish among VWD subtypes.
b
Enhanced platelet agglutination at low-dose ristocetin
Enhanced platelet agglutination at low-dose ristocetin (RIPA) indicates pathologically increased VWF–platelet interaction. This finding is characteristic of type 2B VWD and platelet-type VWD and should prompt further testing to determine whether the abnormality lies in VWF or in platelet GPIbα.
c
FVIII disproportionately lower than VWF antigen
Disproportionately low FVIII relative to VWF antigen suggests type 2N VWD or hemophilia A rather than type 2B.
d
VWF antigen and activity reduced proportionally
Proportional reduction of antigen and activity is more consistent with a quantitative deficiency such as type 1 VWD.

Why must platelet-type VWD be considered when type 2B VWD is suspected?

a
Both are caused by absent VWF.
Neither disorder is characterized by absent VWF.
b
Platelet-type VWD is another name for type 2B VWD.
Although the laboratory findings may overlap, platelet-type VWD and type 2B VWD are distinct disorders.
c
Platelet-type VWD is caused by defective FVIII binding
Defective FVIII binding is the hallmark of type 2N VWD.
d
Both produce increased VWF–platelet interaction, but the defect is on different sides of the interaction.
Type 2B VWD results from gain-of-function variants in VWF that increase binding to platelet GPIbα. Platelet-type VWD produces a similar phenotype because the abnormality is in the platelet receptor rather than in VWF itself. Distinguishing the two is important for diagnosis, genetic counseling, and management.

A patient has FVIII 18 IU/dL, VWF antigen 72 IU/dL, platelet-dependent VWF activity 68 IU/dL, and normal multimers. What is the most important next diagnostic consideration?

a
Type 2N VWD or mild hemophilia A
This pattern is characterized by FVIII that is disproportionately low relative to the amount of VWF present. That finding should immediately raise suspicion for type 2N VWD or mild hemophilia A, because both disorders produce low FVIII despite relatively preserved VWF.
b
Type 2A VWD
Type 2A VWD usually produces reduced platelet-dependent activity relative to antigen together with loss of high-molecular-weight multimers.
c
Type 2B VWD
Type 2B VWD is characterized by increased platelet binding, often enhanced low-dose RIPA, and sometimes thrombocytopenia.
d
Type 3 VWD
Type 3 VWD is characterized by virtual absence of VWF rather than normal VWF antigen and activity.

Why can type 2N VWD be mistaken for mild hemophilia A?

a
Both are caused by abnormal platelet GPIbα.
Abnormal platelet GPIbα characterizes platelet-type VWD, not type 2N.
b
Both may present with low FVIII activity.
Both disorders can present with low FVIII activity and bleeding after trauma or surgery. The difference is that hemophilia A results from an F8 defect, whereas type 2N VWD results from defective FVIII binding to VWF.
c
Both always have absent VWF multimers.
VWF multimers are usually normal in type 2N VWD.
d
Both show enhanced low-dose RIPA.
Enhanced low-dose RIPA suggests increased VWF–platelet interaction, not impaired FVIII binding.

Which statement about type 2B VWD is most accurate?

a
Thrombocytopenia is required for diagnosis.
Thrombocytopenia is common but not universal in type 2B VWD.
b
High-molecular-weight multimers are always absent.
Some patients retain high-molecular-weight multimers despite increased platelet binding.
c
Desmopressin is generally avoided because it may worsen VWF–platelet binding and thrombocytopenia.
Desmopressin may release additional abnormal VWF into the circulation and can worsen platelet binding and thrombocytopenia in type 2B VWD. For this reason, it is generally avoided unless exceptional circumstances exist under specialist supervision.
d
FVIII-only replacement is preferred.
FVIII-only replacement does not address the underlying VWF abnormality.

A patient is labeled as having type 2A VWD because of a low activity-to-antigen ratio, but multimer analysis shows preserved high-molecular-weight multimers. What is the best interpretation?

a
The diagnosis should be reconsidered, particularly type 2M VWD.
A low activity-to-antigen ratio with preserved high-molecular-weight multimers is the classic pattern for type 2M VWD. Multimer analysis helps distinguish loss of architecture (type 2A) from preserved architecture with impaired binding (type 2M).
b
The patient must have type 3 VWD.
Type 3 VWD is characterized by virtual absence of VWF rather than preserved multimers.
c
Preserved multimers confirm type 2A VWD.
Loss, not preservation, of high-molecular-weight multimers supports type 2A VWD.
d
VWD has been excluded
The laboratory findings still indicate qualitative VWF dysfunction.

Which patient most clearly needs a VWF collagen-binding assay or genetic testing to clarify classification?

a
A patient with absent VWF antigen and FVIII 2 IU/dL
This pattern strongly suggests type 3 VWD rather than an isolated collagen-binding abnormality.
b
A patient with normal platelet-dependent VWF activity but bleeding symptoms suggesting a collagen-binding defect
Some type 2M variants primarily impair collagen binding rather than platelet binding. When bleeding symptoms are convincing but standard platelet-dependent VWF assays are relatively preserved, collagen-binding assays or targeted genetic testing may identify the underlying defect.
c
A patient with proportional reductions in VWF antigen and activity
Proportional reduction of antigen and activity is more consistent with quantitative deficiency.
d
A patient with isolated prolonged PT
Isolated prolongation of the PT suggests a disorder of the extrinsic coagulation pathway rather than VWD.

Which statement best summarizes treatment logic in type 2 VWD?

a
Treat all type 2 variants the same because they are all qualitative disorders.
The four type 2 subtypes have different mechanisms and different treatment implications.
b
Desmopressin is always first-line therapy in every type 2 subtype.
Desmopressin responsiveness varies among type 2 variants and is generally avoided in type 2B VWD.
c
VWF antigen level alone determines treatment intensity.
Proportional reduction of antigen and activity is more consistent with quantitative deficiency.
d
Base therapy on subtype, bleeding phenotype, previous treatment response, and the hemostatic challenge.
VWF antigen alone does not capture qualitative dysfunction or predict procedural bleeding risk.

Sort each clue into the type 2 VWD subtype it most strongly suggests.

enhanced low-dose RIPA
loss of high-molecular-weight multimers with low activity-to-antigen ratio
preserved high-molecular-weight multimers with low platelet-dependent activity-to-antigen ratio
increased susceptibility to ADAMTS13-mediated loss of large multimers
selective collagen-binding defect with preserved platelet-dependent activity
thrombocytopenia that worsens after desmopressin
Type 2A
Type 2B
Type 2M

Matching prompt: Match the subtype with the failed VWF job.

Type 2N
Type 2A
Type 2B
VWF cannot bind and stabilize FVIII normally
VWF lacks the large multimer architecture needed for optimal platelet adhesion
VWF binds platelet GPIbα too avidly
Correct! Sorry, Incorrect.

Closing Note

Type 2 VWD is qualitative disease. The protein may be present, but a job has failed. The clinician’s task is not to memorize four labels, but to find the failed function.

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