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10 Variations in size and color of erythrocytes

Variations in size

FIGURE 10–1A Microcytes (MCV < 80 fL.).

Associated with:

Iron deficiency anemia, thalassemia minor, chronic inflammation (some cases), lead poisoning, hemoglobinopathies (some), sideroblastic anemia

Normal erythrocytes are approximately the same size as the nucleus of a small lymphocyte.

FIGURE 10–1C Macrocytes (MCV > 100 fL.).

FIGURE 10–1B Normocytes (MCV 80-100 fL.).

Associated with:

Liver disease, vitamin B₁₂ deficiency, folate deficiency, neonates, reticulocytosis

Anisocytosis is the variation in red blood cell (RBC) diameter (or RBC volume) on a blood film. This variation correlates with the electronically determined red blood cell distribution width (RDW). An RDW greater than 14.5% indicates a heterogenous population of RBCs and a variety of sizes of RBCs should be seen. A low RDW is of no significance.

Anisocytosis

FIGURE 10–2A Heterogeneous population of erythrocytes, indicating anisocytosis (RDW > 14.5%).

Associated with:

Anemias, especially iron deficiency, megaloblastic and hemolytic

FIGURE 10–2B When two distinct populations of RBCs are seen, it is termed a dimorphic population (RDW > 14.5%).

Associated with:

Transfusion, myelodysplastic syndromes, vitamin B₁₂, folate, or iron deficiencies—early in treatment process

Variation in color of erythrocytes

FIGURE 10–3A Hypochromia. The central pallor zone of the erythrocyte must be greater than one-third of the diameter of the cell before it is classified as hypochromic. (Note: the MCHC, not the MCH, should be used as a gauge of hypochromia; however, the MCHC is not always decreased when few hypochromic cells are seen.)

FIGURE 10–3B Dichromic population of erythrocytes. (Two populations of RBCs are shown: one normochromic and one hypochromic.)

FIGURE 10–3C Polychromasia; retained RNA in RBCs.

FIGURE 10–3D Normochromic erythrocytes. (MCHC 32-36 g/dL or 32%-36%.) For comparison with hypochromic and polychromatic erythrocytes.

Associated with:

Iron deficiency anemia, thalassemias, sideroblastic anemia, lead poisoning, some cases of anemia of chronic inflammation.

Associated with: 

Acute and chronic hemorrhage, hemolysis, effective treatment for anemia, neonates.

Associated with:

Transfusions, sideroblastic anemia.

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10 Variations in size and color of erythrocytes

Variations in size

FIGURE 10–1A Microcytes (MCV < 80 fL.).

Associated with:

Iron deficiency anemia, thalassemia minor, chronic inflammation (some cases), lead poisoning, hemoglobinopathies (some), sideroblastic anemia

Normal erythrocytes are approximately the same size as the nucleus of a small lymphocyte.

FIGURE 10–1C Macrocytes (MCV > 100 fL.).

FIGURE 10–1B Normocytes (MCV 80-100 fL.).

Associated with:

Liver disease, vitamin B₁₂ deficiency, folate deficiency, neonates, reticulocytosis

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Clinical Hematology Atlas