What is the Difference Between Anisocytosis and Poikilocytosis

The main difference between anisocytosis and poikilocytosis is that anisocytosis is the presence of red blood cells of varying sizes in a blood smear whereas poikilocytosis is the presence of red blood cells of varying shapes. Furthermore, the two conditions of anisocytosis are macrocytosis and microcytosis while poikilocytosis results in flatter, elongated, crescent-shaped, or teardrop-shaped, and other abnormal features like pointy projections in red blood cells.

Anisocytosis and poikilocytosis are two clinical conditions of red blood cells recognized in blood smears. Furthermore, anisopoikilocytosis refers to an overlapped condition of both anisocytosis and poikilocytosis.

Key Areas Covered

1. What is Anisocytosis
     – Definition, Symptoms, Causes
2. What is Poikilocytosis
     – Definition, Symptoms, Causes
3. What are the Similarities Between Anisocytosis and Poikilocytosis
    – Outline of Common Features
4. What is the Difference Between Anisocytosis and Poikilocytosis
    – Comparison of Key Differences

Key Terms

Anisocytosis, Anisopoikilocytosis, Blood Smear, Poikilocytosis, Red Cell Size, Red Cell Shape

What is Anisocytosis

Anisocytosis is a clinical condition characterized by the presence of red blood cells varying in size. Under normal conditions, a person should have equal-sized red blood cells. Macrocytosis and microcytosis are the two observable conditions in anisocytosis. Macrocytosis is the presence of red blood cells larger than the normal size while microcytosis is the presence of red blood cells smaller than the normal size. In some conditions, red blood cells with both macrocytosis and microcytosis can be observed.

Figure 1: Anisocytosis

Generally, the main causes for anisocytosis are iron deficiency anemia, sickle cell anemia, autoimmune hemolytic anemia, megaloblastic anemia, pernicious anemia, and thalassemia. Also, some other disorders including myelodysplastic syndrome, chronic liver disease, and disorders of the thyroid can cause anisocytosis. In addition, folate or vitamin B12 deficiency can cause macrocytosis. Instead of blood smears, the red cell distribution width (RDW) can be considered as a measurement of anisocytosis. Here, the red cell distribution width can be calculated as a coefficient of variation of the distribution of RBC volumes divided by the mean corpuscular volume (MCV).

What is Poikilocytosis

Poikilocytosis is another clinical condition, containing abnormally-shaped red blood cells in a blood smear. Generally, the red blood cells of a normal individual are disk-shaped with a flattened center on both sides. However, poikilocytosis results in red blood cells, which are flatter, elongated, crescent-shaped, or teardrop-shaped, and other abnormal features like pointy projections when compared to the normal red blood cells.

Figure 2: Poikilocytes

Moreover, inherited causes of poikilocytosis include sickle cell anemia, thalassemia, pyruvate kinase deficiency, McLeod syndrome, hereditary elliptocytosis, and hereditary spherocytosis. On the contrary, acquired causes of poikilocytosis include iron-deficiency anemia, autoimmune hemolytic anemia, megaloblastic anemia, live and kidney disease, alcoholism, lead poisoning, cancer-related chemotherapy treatments, etc.

Similarities Between Anisocytosis and Poikilocytosis

• Anisocytosis and poikilocytosis are two clinical conditions of red blood cells observed in blood smears.
• Different forms of anemia, as well as thalassemia, cause these blood disorders. Therefore, the causes of these disorders can be either inherited or acquired.
• Also, both cause deficiency of carrying oxygen to various tissues of the body.
• Furthermore, the common symptoms of both are weakness, fatigue, pale skin, and shortness of breath.
• Besides, anisopoikilocytosis is a combined situation of both anisocytosis and poikilocytosis.

Difference Between Anisocytosis and Poikilocytosis

Definition

Anisocytosis refers to a medical term meaning that a patient’s red blood cells are of unequal size while poikilocytosis refers to an increase in abnormal red blood cells of any shape where they make up 10% or more of the total population. Thus, this is the main difference between anisocytosis and poikilocytosis.

Presentation in a Blood Smear

While anisocytosis results in macrocytosis and microcytosis, poikilocytosis results in flatter, elongated, crescent-shaped, or teardrop-shaped, and other abnormal features like pointy projections in red blood cells. Hence, the presentation in a blood smear is an important difference between anisocytosis and poikilocytosis.

Diagnosis

Moreover, diagnosis is also a difference between anisocytosis and poikilocytosis.  Red cell distribution width (RDW) is the measurement of anisocytosis while poikilocytosis is basically diagnosed through blood smears.

Conclusion

Anisocytosis is a blood disorder with varying sizes of red blood cells. In comparison, poikilocytosis is a blood disorder with varying shapes of red blood cells. Hence, the main difference between anisocytosis and poikilocytosis is the type of changes in red blood cells. More importantly, both anemia and thalassemia cause these disorders. They result in the deficiency of oxygen transport to the tissues of the body. 

References:

1. Falck, Suzanne. “Anisocytosis: Causes, Diagnosis, and Treatment.” Healthline, Healthline Media, 15 Sept. 2017, Available Here.
2. Biggers, Alana. “Poikilocytosis: Symptoms, Treatment, Outlook, and More.” Healthline, Healthline Media, 25 Oct. 2017, Available Here.

Image Courtesy:

1. “Anisocytosis” By Dr Graham Beards – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “Poikilocytes” By Dr Graham Beards – Own work (CC BY-SA 3.0) via Commons Wikimedia