Molecular testing to confirm a phenotypic diagnosis of von Willebrand disease type 2M.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA) or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Mucocutaneous bleeding after brushing or flossing teeth, unexplained bruising, prolonged repeated nosebleeds, menorrhagia, and prolonged bleeding following childbirth, trauma or surgery.
Incidence: Approximately 1 in 100 to 1 in 1000 individuals.
Inheritance: Autosomal dominant for type 2M.
Penetrance: Dominant mutations are incompletely penetrant when VWF:Ag and VWF:RCo levels are 25-50 IU/dL. Full penetrance is expected when VWF:Ag and VWF:RCo levels are less than 25 IU/dL.
Cause: Pathogenic VWF mutations in exons 28, 30, and 31.
Clinical Sensitivity: 80 percent for vWD types 2A, 2B, and 2M; unknown for other vWD subtypes.
Methodology: Bidirectional sequencing of VWF exons 28, 30, 31 and its intron-exon boundaries.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations, deep intronic mutations, and large deletion/duplications will not be detected. Mutations lying outside of VWF exons 28, 30, and 31 will not be evaluated.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|2005491||vWD Type 2M (VWF) Sequencing Specimen|
|2005492||vWD Type 2M (VWF) Sequencing Interp|
- VWD type 2M sequencing assay
- VWF2M Sequencing