Conference Coverage

Researchers seek better understanding of von Willebrand disease


 

EXPERT ANALYSIS FROM THSNA 2018

– Several groups of researchers are examining cohorts of von Willebrand disease (VWD), looking at its pathogenesis and molecular causes, as well as ways to improve treatment strategies.

At the biennial summit of the Thrombosis & Hemostasis Societies of North America, Robert F. Sidonio Jr., MD, MSc, highlighted the efforts underway, including the Zimmerman Program for the Molecular and Clinical Biology of VWD study (ZPMCB-VWD), a large grant project funded by the National Institutes of Health.

At the time of publication, there were more than 700 index cases and more than 2,200 families in the study. It includes data from 8 primary centers and 23 secondary centers. The goals are to characterize the molecular causes of VWD and the examine the fidelity of diagnosis, “which is a critical component of the study,” said Dr. Sidonio, clinical director of the hemostasis/thrombosis program at Children’s Healthcare of Atlanta.

Dr. Robert F. Sidonio Jr., clinical director of the hemostasis/thrombosis program at Children’s Healthcare of Atlanta Doug Brunk/MDedge News

Dr. Robert F. Sidonio Jr.

The ZPMCB-VWD cohort demonstrated 74% of subjects to have VWF sequence variations when immunological assays of von Willebrand factor (VWF:Ag) levels were less than 40 IU/dL (Hematology Am Soc Hematol Educ Program. 2014; 2014[1]:531-5). The precise cutoff varies by study, with VWF:Ag levels below 20-40 IU/dL most strongly correlated with presence of a VWF sequence variation.

When the ZPMCB-VWD investigators examined the correlation of bleeding phenotype and the genotype, the found that as the level of VW factor goes down, the bleeding score generally goes up, but it becomes a little bit flat in the 20-30 IU/dL range.

“Where we spend a lot of our time is with patients who have levels of 30%-50%, which can be quite heterogeneous,” Dr. Sidonio said.

Another finding made out of the ZPMCB-VWD project was the discovery of the single nucleotide polymorphism p.D1472H, which was noted to be more common in African American patients and leads to low Von Willebrand Ristocetin Cofactor (VWF:RCo) and VWF:RCo/VWF:Ag ratio, but does not increase the bleeding score.

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