What is the main cause of Thrombocytopenic purpura (TTP)?

The main cause of Thrombocytopenic purpura (TTP) is the presence of autoantibodies to the von Willebrand factor-cleaving protease known as ADAMTS13. In TTP, these autoantibodies lead to a deficiency in functional ADAMTS13, which is crucial for cleaving large von Willebrand factor (vWF) multimers into smaller, less adhesive forms. When this protease is deficient, large vWF multimers accumulate, promoting excessive platelet aggregation and leading to microangiopathic hemolytic anemia and a low platelet count (thrombocytopenia).

This underlying mechanism causes the characteristic features of TTP, including the formation of small blood clots throughout the microcirculation, resulting in a range of clinical symptoms such as purpura, neurologic symptoms, and renal dysfunction. Because the autoantibodies specifically target ADAMTS13, their presence is central to the pathophysiology of TTP, setting it apart from other conditions that might cause thrombocytopenia or purpura.