Poikilocytosis: Most Common Types & Main Causes

Poikilocytosis refers to an abnormal shape of red blood cells circulating in the blood. They can be rounded in the shape of a sphere, teardrop, sickle or spiculated, all which can interfere with normal red blood cell functioning.

Red blood cells typically have a rounded shape, are flattened and have a lighter central region in the center due to the distribution of hemoglobin. However, some conditions can cause changes in the red blood cell membrane, resulting in the appearance of an abnormal cell shape.

The main abnormal shapes identified in the microscopic evaluation of blood are drepanocytes (sickle cells), dacryocytes (tear drops), elliptocytes (elongated) and codocytes (a shooting target with a bullseye).

Common types

Poikilocytosis can be observed microscopically through a blood smear, and can include the following abnormal shapes:

• Spherocytes, in which the red blood cells are round and smaller than normal red blood cells;
• Dacryocytes, which are teardrop-shaped red blood cells;
• Acanthocyte, in which the red blood cells have a spiculated or spiky membrane
• Codocytes, also calledtarget cells, which are target-shaped due to the distribution of hemoglobin;
• Elliptocytes, in which red blood cells have an oval, elongated shape;
• Drepanocytes, which are sickle-shaped red blood cells that appear mainly in sickle cell anemia;
• Stomatocytes, which are red blood cells that have a narrow area in the center, similar to a mouth;
• Schizocytes, in which the red blood cells have an undefined shape.

Poikilocytosis that is identified during the microscopic examination is typically s indicated in the results report. The type of of poikilocytosis is important to know, as it guides the doctor's follow-up assessment and further testing to determine a diagnosis. 

Main causes

Poikilocytosis appear as a consequence of changes related to red blood cells, such as biochemical changes in the membrane, metabolic changes in enzymes, abnormalities related to hemoglobin and aging of red blood cells. These changes can occur in several diseases, resulting in poikilocytosis.

The most common causes of poikilocytosis include:

1. Sickle cell anemia

Sickle cell anemia is a disease characterized mainly by a change in the shape of the red blood cell. This happens due to the mutation of one of the chains that form hemoglobin, which reduces the hemoglobin's ability to bind to oxygen and, consequently, transport it to organs and tissues. This makes it more difficult for red blood cells to pass through the veins.

As a result of the change in shape and the decrease in oxygen transport, patients with this condition will generally experience excessive fatigue, generalized pain, paleness and delayed growth.

Although sickle cells are characteristic of sickle cell anemia, it is also possible to observe, in some cases, the presence of codocytes.

2. Myelofibrosis

Myelofibrosis is a type of myeloproliferative neoplasm characterized by the presence of circulating dacryocytes in peripheral blood. The presence of dacryocytes is most often an indication that there are changes in the bone marrow, which is what happens in myelofibrosis.

Myelofibrosis is characterized by mutations that lead to the way cells are produced in the bone marrow. This conditions leads to an increase in the number of mature cells in the bone marrow, which promote the formation of scars in the marrow. Overtime, this scarring decreases normal functioning.

3. Hemolytic anemias

Hemolytic anemias are characterized by the production of antibodies that attack and destroy red blood cells. It leads to the appearance of typical anemia symptoms, such as fatigue, paleness, dizziness and weakness. As a consequence of the destruction of red blood cells, there is an increased production of blood cells by the bone marrow and spleen, which may result in the production of abnormal red blood cells, such as spherocytes and elliptocytes.

4. Liver diseases

Diseases that affect the liver can also lead to the appearance of poikilocytosis, notably the presence of stomatocytes and acanthocytes. This finding typically prompts further testing to check liver functioning to determine the underlying abnormality in the liver.

5. Iron deficiency anemia

Iron deficiency anemia is characterized by a decrease in the amount of hemoglobin circulating in the body and, consequently, a decrease in oxygen levels. Iron is essential for the formation of hemoglobin, which transports oxygen to the tissue.

Low hemoglobin levels causes symptoms such as weakness, tiredness, lack of motivation and fainting. Untreated iron deficiency anemia can favor the appearance of poikilocytosis, particularly the presence of codocytes.