A VWD Treatment Oddity

A VWD Treatment Oddity
Jan 15, 2016 5:59am

A colleague told George about what seems like an unusual subtype 2A von Willebrand disease case. When treating with Humate P, the VWF antigen (VWF :Ag) level rises as expected, however the VWF ristocetin cofactor (VWF :RCo) activity level consistently hovers at 20–30%. Those are all the facts available. Could this be a VWF inhibitor specific for activity only?

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A colleague told George about what seems like an unusual subtype 2A von Willebrand disease case. When treating with Humate P, the VWF antigen (VWF :Ag) level rises as expected, however the VWF ristocetin cofactor (VWF :RCo) activity level consistently hovers at 20–30%. Those are all the facts available. Could this be a VWF inhibitor specific for activity only?

By George Fritsma
Jan 16, 2016 7:36am
From Rajiv Pruthi, MD, Mayo Medical Laboratories: Hello George, Thanks for reaching out with this interesting question.
I have not encountered this situation. Generally, if there is an inhibitor, it is typically a clearing antibody where both the antigen and activity will have a shortened half-life. At our lab, we do run the ristocetin inhibitor screen, but over the years, I have only seen one positive case, it is possible that our assay is not sensitive. Does the lab still have samples? Can they run the LIA assay for VWF activity?
By George Fritsma
Jan 25, 2016 1:18pm
Helo Rajiv and George
From John Olson, MD: I can’t really add anything to the comment that Rajiv makes. There is inadequate data. The proposed solution of an antibody that reduces function but not clearance is possible, but would need to be demonstrated. One can think of a number of interesting things to do but without further data, we’ll have to settle for conjecture.

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