Severe deficiency of the specific von Willebrand factor-cleaving protease (ADAMTS 13) activity in a subgroup of children with atypical hemolytic uremic syndrome

Abstract Objective The von Willebrand factor-cleaving protease (VWF-cp) activity has been reported to be deficient in adults with thrombotic thrombocytopenic purpura (TTP) and generally normal in adults with hemolytic uremic syndrome (HUS). The goal of this study was to determine VWF-cp activity in children with typical postdiarrheal (d+) HUS or atypical non-postdiarrheal (d-) HUS. Study design We measured VWF-cp activity in the plasma of 64 children with either (d+) HUS (n = 41) or (d-) HUS (n = 23). Results In the acute phase of HUS, VWF-cp activity was normal (>50%) in 54 children and undetectable ( Conclusion A subgroup of pediatric patients with atypical (d-) HUS, with hematologic symptoms starting at birth and a recurrent course progressively involving kidney and brain, is related to VWF-cp deficiency and actually corresponds to Upshaw-Schulman syndrome revisited as congenital TTP. (J Pediatr 2003;142:310-7)