Sékouba Sidimé/LinkedIn
Jun 2, 2026, 19:42
Sékouba Sidimé: vWD vs Hemophilia A – The Classic USMLE Step 1 trap in Hematology
Sékouba Sidimé, Internal Medicine Physician, shared a post on LinkedIn:
“vWD vs Hemophilia A – The No. 1 USMLE Step 1 trap in Hematology
One lab result tells them apart.Here’s what you need to know:
von Willebrand Disease
- Prolonged aPTT, prolonged Bleeding time, decreased Ristocetin
- Female with a family history and mucocutaneous bleeding
- Treatment: Desmopressin (DDAVP)
Hemophilia A
- Prolonged aPTT , Bleeding time normal, Ristocetin normal
- Male with hemarthroses
- Treatment: Factor VIII replacement
The key:
vWF carries Factor VIII — decreased vWF results in secondary reduction of Factor VIII.
That’s why vWD affects both aPTT AND bleeding time.
Hemophilia A affects aPTT only.
If the examiner mentions Ristocetin then think vWD. Every time.”

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