Reduced von Willebrand factor-cleaving protease levels in secondary thrombotic microangiopathies and other diseases.

Thrombotic thrombocytopenic purpura (TTP) is a severe multisystem thrombotic microangiopathy (TMA). Significant advances have been made in understanding the pathogenesis of TTP since the discovery of ADAMTS-13 ( A Disintegrin And Metalloproteinase with Thrombo Spondin-1-like domains), the enzyme that regulates the size of von Willebrand factor (VWF) multimers. The inherited forms of TTP are mainly caused by a severe ADAMTS-13 deficiency, yet many aspects of the complex biological relationships between VWF-cleaving metalloproteinase and acquired TMA are still unclear. This latter issue will be critically addressed in this review article. In addition, the published literature evaluating plasma ADAMTS-13 levels in other pathologic conditions different from TMA will also be discussed.