The Production of Schistocytes by Fibrin Strands

By Bm N S. Bin L AND IRvIN N. KUHN A FORM OF HEMOLYTIC ANEMIA characterized by thrombocytopenia and the presence of fragmented red cells in the peripheral blood has been called microangiopathic hemolytic anemia by Brain, Dacie and Hourihane.’ These workers showed that in this disease the amount of hemoglobinemia and the degree of erythrocyte fragmentation correlated closely with the severity of microangiopathy. This microangiopathy, most prominent in the kidneys, was characterized by fibrinoid necrosis of the arterioles, necrotizing arteritis, and the presence of intraluminal hyalin thrombi. When intravascular coagulation is precipitated in animals under appropriate experimental conditions, fragmented erythrocytes and a microangiopathy are produced.24 The tissue from these experiments provides strong evidence that erythrocyte fragments or schistocytes result when rapidly moving red cells encounter fine fibrin strands. Acute defibrination in animals initially causes the formation of large numbers of microclots composed of very fine fibrin strands. Subsequently a microangiopathy results, with similar histology to that found in postmortem kidney sections of patients who, during life, exhibited the classical symptoms of microangiopathic hemolytic anemia. Despite this considerable body of evidence incriminating fine fibrin strands as the major etiologic factor in schistocyte production, these strands are rarely observed postmortem in humans. Bull and Brain in a study of experimental models of microangiopathic hemolytic anemia suggested that the fine fibrin strands, being the most delicate of the clot components, would be the first to undergo lysis at death.5 The patient herein described suffered from severe microangiopathic hemolytic anemia during life and at death his vasculature contained large numbers of microclots composed of fine fibrin strands. This case is presented in some detail because it documents the essential identity of the pathogenesis of microangiopathic hemolytic anemia in man with the hemolytic anemia that accompanies induced intravascular coagulation in animals.