[Thrombotic Thrombocytopenic Purpura --Pathophysiology and Assays of ADAMTS13 Activity]

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder classified with a type of thrombotic microangiopathy (TMA). TTP is caused by a deficiency of von Willebrand factor-cleaving protease called ADAMTS13 (a disintegrin-like and metalloprotease with a thrombospondin type1 motif 13). Low ADAMTS13 levels result in increased ultra-large von Willebrand factor multimers (UL-VWFM), which induce platelet adhesion and thrombosis. Congenital TTP (Upshaw-Schulman syndrome: USS) is an inherited disorder of ADAMTS13, and the other more commonly is an acquired TTP caused by autoantibodies against ADAMTS13. This article reviews the progress of ADAMTS13 activity measurement and the resulting changes in the diagnosis and treatment of TTP.