Microangiopathic and Vascular Disorders

The thrombotic microangiopathies are characterized by microangiopathic hemolytic anemia and thrombocytopenia and can be classified as autoimmune, drug induced, complement mediated, and infectious/other. Reaching a definitive diagnosis for these disorders can be challenging due to the similarity of presenting symptoms and laboratory findings. Specific disorders described in this review include thrombotic thrombocytopenic purpura, the hemolytic-uremic syndrome, thrombotic microangiopathies of pregnancy (including preeclampsia and HELLP syndrome), disseminated intravascular coagulation, and antiphospholipid syndrome. Vascular disorders that lead to hematologic abnormalities are also discussed. Figures show the major classifications of the thrombotic microangiopathies; ADAMTS13 activity in normal and thrombotic thrombocytopenic purpura plasma; a fragmented red blood cell (arrow), also known as a schistocyte or helmet cell; major considerations in the initial treatment of thrombotic thrombocytopenic purpura and options for refractory patients as well as treatment considerations after discontinuation of plasma exchange; and a diagram of the complement pathway showing regulatory proteins