Patient Test Information

Blood Smear_ Details on RBCs, WBCs

Details: Red Blood Cell Irregularities


  • Anisocytosis: this is a variation in size of RBCs; it may be an indication of anemia
  • Macrocytosis: large RBCs that may be due to a vitamin B12 or folate deficiency. They are seen in megaloblastic anemia (e.g., pernicious anemia), chronic alcoholism, liver disease, thyroid disease, and myelodysplastic syndrome.
  • Microcytosis: this is the presence of small RBCs that is commonly due to an iron deficiency anemia or to an inherited disorder such as thalassemia.


  • Poikilocytosis is a variation in the shape of RBCs and may include several different abnormalities at the same time.
  • Acanthocytes (spur or spiculated cells): irregular shaped cells with 5-10 spicules; may be present in the blood of people who have had their spleen removed (splenectomy) or with liver disease. They are also present in an inherited disorder called abetalipoproteineimia.
  • Echinocytes (burr or crenated): may have 10-30 blunt projections and often are seen in people with renal failure; may be an artifact - something caused during sample preparation.
  • Elliptocytes (ovalocyte): elliptical-shaped RBCs seen in hereditary elliptocytosis and various anemias, myelofibrosis.
  • Fragmented cells (schistocytes, helmet cells): fragmented RBCs of various shapes that may be seen in people with disseminated intravascular coagulation (DIC), hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, or a vascular artificial device (prosthesis) such as a mechanical heart valve.
  • Rouleaux: RBCs that appear as a stack of coins and are seen in people with multiple myeloma or Waldenstrom macroglobulinemia because of increased serum proteins.
  • Sickle cells: crescent-shaped RBCs that are characteristic of sickle cell anemia.
  • Target cells: RBCs that resemble a bull's-eye; commonly seen in people with abnormal inherited forms of hemoglobin (hemoglobinopathies), thalassemia, various anemias and liver disease.
  • Teardrop cells (dacrocytes): RBCs that resemble a teardrop; often seen in people with myelofibrosis and thalassemia.
  • Spherocytes: sphere-shaped RBCs that are often present in immune hemolytic anemia or hereditary spherocytosis.


  • Hypochromia/hypochromasia: this may be seen in a variety of disorders, including thalassemia and iron deficiency. The RBC is pale in color due to insufficient hemoglobin and contains a large, hollow middle (central pallor) of the cell.
  • Hyperchromia/hyperchromasia: the RBC is darker in color than normal due to a greater than normal concentration of hemoglobin within the cell; this may be due to dehydration or presence of spherocytes.
  • Polychromasia: blue-staining RBCs reflecting increased RNA content, indicating that they are immature due to early release from the bone marrow.

Abnormal structures within the red blood cell

  • Nucleated RBCs (NRBC, normoblasts): an immature form of RBCs seen when there is increased demand for RBCs to be released by the bone marrow, or when there is marrow involvement by fibrosis or tumor; may be seen in severe anemia, myelofibrosis, thalassemia, miliary tuberculosis, cancers that involve the bone marrow, and in chronic low oxygen levels (hypoxemia). Nucleated RBCs can be normal in infants for the first two or three days after birth.
  • Reticulocytes: these are immature RBCs that are usually a blue-staining (polychromatic) color. A few of these young red blood cells are normal in the circulation, but they may be present in elevated numbers with acute blood loss, hypoxia, RBC destruction, sickle cell disease, glucose-6-phosphate. dehydrogenase (G6PD) deficiency, and autoimmune hemolytic anemia.
  • Siderocyte, sideroblast, ring sideroblast: When RBCs are stained with Prussian blue dye, iron granules may be seen. Sideroblasts are immature siderocytes and may actually form a ring pattern indicative of sideroblastic anemia.
  • Basophilic stippling (punctate basophilia) is dark blue dots inside the RBC; due to abnormal aggregation of ribosomes and polyribosomes and may be present in heavy metal intoxication (such as lead), thalassemia and many other anemias.
  • Heinz bodies: large inclusion bodies (granules) in the RBCs when stained with a supravital stain like crystal violet; often seen in the setting of an enzyme (G6PD) deficiency, drug-induced hemolysis, or unstable hemoglobin disease.
  • Howell-Jolly bodies (small, round remnants of nuclear DNA inside cell): present in sickle cell anemia, hemolytic or megaloblastic anemias, and may be seen after a splenectomy.
  • Cabot ring: uncommon threadlike inclusions that form a loop or figure-of-eight structure within the RBC; may be seen in a variety of anemias.
  • Malarial parasites: in people with malaria, these parasites live inside RBCs and may be visible on a blood smear. This is not a routine finding; these parasites are usually found in those who live in or have traveled to areas where the disease is endemic.