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Updated: Aug 5, 2026

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
Published on: September 9, 2012
Deficient activity of von Willebrand factor-cleaving protease in patients with Upshaw-Schulman syndrome
Y Sasahara1, S Kumaki, Y Ohashi
1Department of Pediatric Oncology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Miyagi, Japan.
Abstract:
We identified unusually large von Willebrand factor (vWF) multimers caused by deficient activity of vWF-cleaving protease in 2 patients with Upshaw-Schulman syndrome. The autoantibodies that inhibited the protease activity were not detected in the plasma of either patient. Periodic fresh-frozen plasma transfusion was effective for management of the hemolysis and thrombocytopenia. We detected enriched enzyme activity in a particular plasma fraction, although molecular cloning of this specific protease is needed to determine a more detailed pathogenesis and to develop new therapeutic approaches.
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