ADAMTS13 and congenital thrombotic thrombocytopenic purpura: Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease with 90% mortality and is characterized by microangiopathic hemolytic anemia, severe thrombocytopenia, neurological abnormalities, fever, and renal insufficiency.[1] Inherited mutations in the ADAMTS13 gene or autoantibodies against ADAMTS13 contribute to the deficiency of ADAMTS13 activity, which leads to the formation of disseminated microvascular platelet thrombi that are attributed to unusually large multimers of von Willebrand factor that cannot be cleaved in the circulation.