What is anisopoikilocytosis?

Anisopoikilocytosis is when you have red blood cells that are of different sizes and shapes.

The term anisopoikilocytosis is actually made up of two different terms: anisocytosis and poikilocytosis. Anisocytosis means that there are red blood cells of varying sizes on your blood smear. Poikilocytosis means that there are red blood cells of varying shapes on your blood smear.

Results from a blood smear can also find mild anisopoikilocytosis. This means that the amount of red blood cells showing varying sizes and shapes is more moderate.

Anisopoikilocytosis means having both anisocytosis and poikilocytosis. Therefore, it’s helpful to first break down the causes of these two conditions individually.

Causes of anisocytosis

The abnormal red blood cell size observed in anisocytosis can be caused by several different conditions:

Causes of poikilocytosis

Causes of the abnormal red blood cell shape seen in poikilocytosis can also be caused by a variety of conditions. Many of these are the same as those that can cause anisocytosis:

  • anemias
  • hereditary spherocytosis
  • hereditary elliptocytosis, an inherited disease in which red blood cells are oval or egg-shaped
  • thalassemia
  • folate and vitamin B-12 deficiency
  • liver disease or cirrhosis
  • kidney disease

Causes of anisopoikilocytosis

There’s some overlap between conditions that cause anisocytosis and poikilocytosis. This means anisopoikilocytosis can occur in the following conditions:

  • anemias
  • hereditary spherocytosis
  • thalassemia
  • folate and vitamin B-12 deficiency

There are no symptoms of anisopoikilocytosis. However, you can experience symptoms from the underlying condition causing it. Symptoms may include:

  • weakness or lack of energy
  • shortness of breath
  • dizziness
  • quick or irregular heartbeat
  • headache
  • cold hands or feet
  • jaundice, or pale or yellow-colored skin
  • pains in your chest

Some symptoms are associated with specific underlying conditions, such as:


Folate or B-12 deficiency

  • mouth ulcers
  • vision problems
  • a feeling of pins and needles
  • psychological problems, including confusion, memory, and judgment issues

Hereditary spherocytosis or thalassemia

Your doctor can diagnose anisopoikilocytosis using a peripheral blood smear. For this test, a small drop of your blood is placed on a glass microscope slide and treated with a stain. The shape and size of the blood cells present on the slide can then be analyzed.

A peripheral blood smear is often performed along with a complete blood count (CBC). Your doctor uses a CBC to check the different types of blood cells in your body. These include red blood cells, white blood cells, and platelets.

Your doctor may also order tests to assess your hemoglobin, iron, folate, or vitamin B-12 levels.

Some of the conditions that cause anisopoikilocytosis are inherited. These include thalassemia and hereditary spherocytosis. Your doctor may also ask you about your family’s medical history.

Treatment will depend on the underlying condition that’s causing anisopoikilocytosis.

In some cases, treatment may involve changing your diet or taking dietary supplements. This is important when low levels of iron, folate, or vitamin B-12 cause symptoms.

More severe anemia and hereditary spherocytosis may require blood transfusions to treat. A bone marrow transplant could also be performed.

People with thalassemia typically require repeat blood transfusions for treatment. Additionally, iron chelation is often needed. In this procedure, excess iron is removed from the blood following a blood transfusion. Splenectomy (removal of the spleen) may also be required in people with thalassemia.

There can be complications from the underlying condition that’s causing anisopoikilocytosis. Complications can include:

  • pregnancy complications, including early delivery or birth defects
  • heart issues due to quick or irregular heartbeat
  • nervous system issues
  • severe infections in people with thalassemia due to repeated blood transfusions or spleen removal

Your outlook depends on the treatment you receive for the underlying condition causing anisopoikilocytosis.

Some anemias and vitamin deficiencies are easily treatable. Conditions such as sickle cell anemia, hereditary spherocytosis, and thalassemia are inherited. They’ll require treatment and monitoring throughout your lifetime. Talk to your medical team about the treatment options that are best for you.