Endothelial Pathology in Thrombotic Microangiopathies

Introduction Thrombotic microangiopathy is a term for a morphologic lesion characterized by platelet and fibrin thrombi involving the microvasculature. The morphologic lesions thus overlap between hemolytic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP), and the lesions seen in scleroderma and malignant hypertension. HUS/TTP typically involves glomeruli and smaller vessels, whereas scleroderma and malignant hypertension involve interlobular arteries and arterioles. Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) share the morphologic lesion of thrombotic microangiopathy, characterized by platelet thrombi occluding the microvasculature. The HUS and TTP syndromes overlap clinically. Recent evidence indicates differing pathogenesis (see below).