Schistocyte Information and Courses from MediaLab, Inc.

A ten-year-old boy came to a physician's attention because of recent jaundice and icteric sclerae. The immediate laboratory work revealed: Hct 24%(normal 36%-47%), MCV 79.5 fl (normal 78-95fl),RDW 13%(normal 11.5-15.0%). His blood smear findings are reflected in these photomicrographs. Note particularly the spherocytes in the upper picture. Some resemble a half-blister with the other half of the cell containing solidly-staining hemoglobin. These are called eccentrocytes. When present, they should trigger a search for red cell hereditary G-6PD deficiency and the oxidant that triggered hemolysis. These morphological findings are only clues; specific testing for G-6PD deficiency should be performed. The blue arrows in the upper photomicrograph are directed toward solid-staining spherocytes in which the cell membrane is beaded by inclusions wrapped within the cell membrane, suggesting the remains of denatured hemoglobin. Included on the smear is a target cell, several acanthocytes, a smudge cell, and a few schistocytes. The lower photomicrograph is supravital staining of affected red blood cells, verifying the presence of Heinz bodies. This disorder was first recognized during the Korean war in 10% of black American soldiers given the antimalarial drug primiquine.

Schistocyte is a general term for a fragmented red blood cell that may assume various shapes, some with horn-like projections (keratocytes), triangle-forms (triangulocytes), and helmet shapes, as illustrated in the upper photograph. Schistocytes are formed when erythrocytes are forced through a vessel blocked with interlacing fibrin strands and the red cells are sliced into fragments. True schistocytes are devoid of central pallor. These damaged cells continue to circulate while healing their torn edges. Finally, they are removed by the spleen. Bite cells (lower photograph) appear when an abnormal hemoglobin aggregate (Heinz body) is nibbled out of a red cell's cytoplasm by the spleen leaving a bitten apple appearance. Glucose 6-PD deficiency secondary to chemical poisoning or injury by oxidant drugs are settings for Heinz body formation, and the telltale bite cells remain as evidence. Hemolytic anemia associated with severe liver disease is another setting where bite cells are formed.

Two photographs of a peripheral blood smear are submitted for review . The smears are from a 9-month-old baby with a heart valve replacement. In the upper photograph is a nucleated RBC and platelets are decreased. Nucleated red cells and occasional giant platelets indicate an active marrow response. In the process of forcing blood cells through the heart valve, erythrocytes are damaged, schistocytes are formed, and platelets are destroyed leading to thrombocytopenia. In the lower field are schistocytes, acanthocytes, echinocytes (burr cells), spherocytes, and the absence of platelets. The presence of burr cells could represent an artifact of smear preparation, but with the history of valve replacement, the red cell changes are likely the result of red cell damage as the cells circulate through the new valve. This situation is described as Waring Blender Effect because of damage to blood cells passing through the new valve, looking as if they had suffered the onslaught of a blender. Target cells and mild hypochromia may reflect iron deficiency through the loss of iron from destruction of RBC's. Iron loss through red cell destruction may be reflected in some hypochromia.

In a study on the reporting of red blood cell morphology abnormalities conducted in Ontario, Canada (Hookey L, Dexter D, Lee DH, Laboratory Hematology 7:83-88, 2001), fewer than 50% of 33 participants used the same term to describe the quantitative frequency of peripheral blood abnormalities. Seven blood smears, each containing one of several abnormal erythrocytes-- schistocytes, teardrop cells, acanthocytes, and Howell-Jolly bodies--were evaluated by 32 participants. The participants were asked to document their evaluations from a list of quantitative terms. There was a heterogeneity in the use of terms "rare," "slight," "occasional," "few," "mild", "present," "moderate," "many," and "marked." Choices of terms were subjective without points of reference. Guidelines for establishing standardized qualitative estimations of abnormal erythrocytes in the peripheral smear are presented as follows: 1+ = 2 - 4/Oil Immersion Field (OIF) 2+ = 5 - 7/OIF 3+ = 8 - 10/OIF 4+ = >10/OIF. The terms "few," "moderate," "many," and "marked" may be substituted for the 1+ - 4+ grading system, but only when their specific points of reference are universally understood in tandem with the above guidelines. A comment should be triggered if any erythrocyte abnormalities are seen in numbers >3/OIF including, but not limited to, polychromasia, basophilic stippling, nucleated RBC's, and Howell-Jolly bodies. Rouleaux or RBC agglutination are important findings and must be documented.

Schistocytes are red cell fragments which are formed when fibrin strands come in contact with circulating red cells. The strands cut a small piece from the original cell. This is the same mechanism which causes the formation of keratocytes. A schistocyte can be seen in the center of this field.

Two slightly larger fragments can be seen in this slide. One is lower center, and the other is lower right. Two dacryocytes or teardrop cells are seen in the upper center. Several ovalocytes are also present in this field. Schistocytes are seen in the same conditions as keratocytes and have a short survival time in circulation. Schistocytes have somewhat more clinical significance than keratocytes.