Poikilocytes are erythrocytes with abnormal shape. Some poikilocytes have fairly specific diagnostic significance, while other forms are very non-specific. Wherever possible, poikilocytes should be identified as to the specific shape changes that are present, e.g. acanthocyte, echinocytes, etc. However, in some situations, there are so many red cell shapes that the generic term "poikilocytosis" suffices and provides the same information as identifying each red cell shape individually.
Poikilocytes (red blood cells with abnormal shape) have an increased tendency to hemolyze, which is they begin to break down. Since the cell membranes contain unsaturated fats creating an odd shaped cell with membrain corrugation and looking like “bottle caps.” In cases of anemia, oval pearshaped, teardrop shaped, and irregularly shaped red cells may be seen. Hemolysis is the rupture of erythrocytes with release of hemoglobin into the plasma. Schistocytes is the term used to describe cell fragments. The presence of schistocytes in the blood stream indicates that hemolysis is taking place. A great variety of chemical agents can lead to the destruction of erythrocytes if there is exposure to a sufficiently high concentration of the substances. These chemicals include arsenic, lead, benzene, nitrites, and potassium chlorate.