RT Book, Section A1 Scully, Marie A2 Kaushansky, Kenneth A2 Prchal, Josef T. A2 Burns, Linda J. A2 Lichtman, Marshall A. A2 Levi, Marcel A2 Linch, David C. SR Print(0) ID 1178755966 T1 Thrombotic Microangiopathies T2 Williams Hematology, 10e YR 2021 FD 2021 PB McGraw-Hill Education PP New York, NY SN 9781260464122 LK hemonc.mhmedical.com/content.aspx?aid=1178755966 RD 2024/10/08 AB SUMMARYThrombotic microangiopathy is a general term for the combination of microangiopathic hemolytic anemia and thrombocytopenia, often accompanied by signs and symptoms consistent with disseminated microvascular thrombosis. Thrombotic thrombocytopenic purpura (TTP) refers to thrombotic microangiopathy, without an obvious predisposing condition in the majority of cases. TTP is caused by autoantibodies to ADAMTS13 (a disintegrin and metalloprotease with a thrombospondin type 1 motif member 13), a plasma metalloprotease that normally cleaves von Willebrand factor (VWF) and regulates VWF-dependent platelet aggregation. Inherited deficiency of ADAMTS13 causes congenital TTP, which typically responds to plasma infusion. Most patients with acquired TTP respond to plasma exchange and immunosuppressive therapy, although many have relapsing disease. Hemolytic uremic syndrome (HUS) refers to thrombotic microangiopathy that usually causes oliguric or anuric acute kidney injury. Ingestion of Shiga toxin–producing Escherichia coli can cause the most common or “typical” form of HUS that is usually preceded by bloody diarrhea. Inherited or acquired defects in the regulation of the alternative complement pathway cause HUS to be referred to as “atypical” because it occurs without a prodrome of bloody diarrhea. Secondary thrombotic microangiopathy can occur in association with autoimmune disease, metastatic cancer, infections, organ transplantation, and certain drugs. These variants of thrombotic microangiopathy differ in pathogenesis and prognosis but can be difficult to distinguish because their clinical features often overlap.