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Byte+: Primary Hemostasis & Von Willebrand Disease
A 26-year-old female presents with menorrhagia and prolonged bleeding after dental work. Her ISTH-BAT score is 6. Labs reveal a normal platelet count, normal PT, and a normal aPTT. Further testing shows reduced VWF antigen and activity, with a Factor VIII activity of 45%.
High Yield Points:
-Mucocutaneous bleeding pattern --> suspect primary hemostasis defect (VWD/Platelets).
-VWD is the most common inherited bleeding disorder (Autosomal).
-Normal aPTT does not rule out VWD (unless severe).
-Estrogen (pregnancy/OCPs) increases VWF levels --> masks diagnosis.
-Type 2N VWD mimics Hemophilia A (low FVIII, autosomal).
-Ristocetin cofactor assay measures VWF functional activity.
-Type 2B VWD --> thrombocytopenia worsened by Ristocetin/DDAVP.
Additional Concepts:
-ISTH-BAT score >4 in adults suggests bleeding disorder likelihood.
-Acquired Von Willebrand Syndrome --> associated with Aortic Stenosis/Wilms Tumor.
-Hypothyroidism can decrease VWF levels --> correct thyroid first.
-Postpartum hemorrhage common due to rapid fall in estrogen/VWF.
VWD Type | Defect Mechanism | Lab Key Feature |
Type 1 | Quantitative deficiency (partial) | Low Ag, Low Activity (Concordant) |
Type 2A | Qualitative (loss of HMW multimers) | Activity << Antigen (Discordant) |
Type 2B | Qualitative (increased GPIb affinity) | Thrombocytopenia, Aggregates w/ low-dose Ristocetin |
Type 2M | Qualitative (decreased platelet binding) | Activity << Antigen, Multimers normal |
Type 2N | Qualitative (decreased FVIII binding) | Low FVIII (mimics Hemophilia A) |
Type 3 | Quantitative (virtual absence) | Undetectable Ag/Activity, very low FVIII |
Key insights: Mucocutaneous bleeding with normal screening labs strongly suggests Von Willebrand Disease or platelet dysfunction. Diagnosis requires specific VWF antigen and activity assays, keeping in mind that physiologic stress and estrogen can falsely normalize levels.
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Ranjan Pathak
Founder, ReviewBytes