Mayo Clin Proc, January 2003, Vol 78 Running Head 809

Mayo Clin Proc. 2004;79:809 809 © 2004 Mayo Foundation for Medical Education and Research

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Schistocytes on the Peripheral Blood SmearAYALEW TEFFERI, MD, AND MICHELLE A. ELLIOTT, MD

Division of Hematology and Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minn

The presence of schistocytes (fragmented red bloodcells) on the peripheral blood smear suggests red blood

cell injury from damaged endothelium and is a characteris-tic feature of microangiopathic hemolytic anemia. Micro-angiopathic hemolytic anemia is an infrequent cause ofCoombs-negative intravascular hemolytic anemia, and itscauses include thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, disseminated intravascularcoagulation, and defective valvular prosthesis. The plateletcount is normal in microangiopathic hemolytic anemia thatis associated with valvular prosthesis but is often decreasedin both disseminated intravascular coagulation and throm-botic thrombocytopenic purpura. The last two-mentionedconditions may be differentiated by the presence of abnor-mal coagulation factor assays (prolonged prothrombin orpartial thromboplastin time, decreased fibrinogen, in-creased D-dimer, and positive soluble fibrin monomer as-say) in disseminated intravascular coagulation but not inthrombotic thrombocytopenic purpura, at least not in theinitial stages. The possibility of thrombotic thrombocyto-penic purpura/hemolytic uremic syndrome should alwaysbe considered in acute-onset thrombocytopenia, which isoften profound (platelet count, <20 × 109/L), especially inthe presence of either renal insufficiency or fluctuatingneurologic changes because of the need for immediateinstitution of specific therapy (plasma exchange).1-3 In the

current blood smear, the presence of schistocytes is accom-panied by the absence of platelets that suggests the diagno-sis of either thrombotic thrombocytopenic purpura or dis-seminated intravascular coagulation.

1. Elliott MA, Nichols WL. Thrombotic thrombocytopenic purpura andhemolytic uremic syndrome. Mayo Clin Proc. 2001;76:1154-1162.

2. Elliott MA, Nichols WL Jr, Plumhoff EA, et al. Posttransplantationthrombotic thrombocytopenic purpura: a single-center experienceand a contemporary review. Mayo Clin Proc. 2003;78:421-430.

3. George JN, Sadler JE, Lämmle B. Platelets: thromboticthrombocytopenic purpura. Hematology (Am Soc Hematol EducProgram). 2002;315-334.

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