NORMOCYTOSIS AND NORMOCHROMIA: CHARACTERISTICS, ANEMIA - MEDICINE - 2025

Both normocytosis and normochromia are terms used in hematologic studies. Both describe specific characteristics of the red blood cell, referring to its size and color, and are widely used to differentiate the types of anemia or other diseases of the blood.

The prefix normo, applied in both terms, comes from the Latin norm and means "within the rule." Its origin is explained by a special rule or square used by carpenters called "norm". When the pieces of wood were square or at right angles, they were said to be "normal", otherwise they were "abnormal."

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With the passage of time that word was applied to the rest of the things. The word cytosis comes from ancient Greek and is formed by the prefix «kytos» or cell and the ending osis which means formation or conversion. Putting all the components together, normocytosis would mean something like "cell of normal formation."

The word chroma is also of Greek origin. It is obtained by uniting the prefix chroma or khroma - color or pigment - and the suffix ia that provides quality. Therefore normochromia means "of normal color." As can be seen, the two terms have Greco-Latin origin, like many other medical expressions.

characteristics

Although the terms normocytosis and normochromia adduce a normal condition in the shape and color of the erythrocyte, they do not always occur in healthy people or without hematologic disease.

There are several clinical entities of the blood, and of the erythrocyte more specifically, that present with normocytosis and normochromia.

Normocytosis

Normocytosis refers to the presence of medium or normal-sized adult red blood cells. The diameter of these erythrocytes is around 7 µm or microns. This size can vary depending on some conditions, such as the patient's age, activity or associated pathologies, but it is always in a range that oscillates between 5.5 and 8.2 microns.

During the different stages of erythrocyte formation, the final size of the red blood cell is determined. In fact, in some of the stages prior to the adult erythrocyte, this cell can be three times the final size.

For example, the proerythoblast measures between 20 and 25 microns. Basophilic and polychromatophilic erythoblasts are also bulky.

The reticulocyte, or young red blood cell - the final step of erythrocyte development - is already the same size as the adult erythrocyte. The only difference is that it no longer has a nucleus or mitochondria. It is during morphological development when changes in the final size of the red blood cell can occur, usually due to iron deficiency.

Normochromia

Normochromia is the presence of red blood cells whose color is normal. Usually the proper coloration of the red blood cell is due to the presence of a normal amount of hemoglobin inside. The tonality of the color will depend on the staining technique used for its study.

Hemoglobin is a special protein in the blood that carries oxygen and also serves as a pigment, giving the red blood cell its characteristic red color.

It will then be the amount of hemoglobin within the erythrocyte that will determine its color, in normal or pathological states.

For the aforementioned, logic dictates that when there is a low amount of hemoglobin, there will be hypochromia. In this case, the erythrocyte looks pale.

In the opposite scenario, when the amount of hemoglobin is high, there will be hyperchromia and the inside of the red blood cell will be darker or even violet in color to the naked eye.

Normochromic normocytic anemia

As explained in the previous section, the fact that there is normocytosis and normochromia does not necessarily mean that the person is healthy. This fact is so true that one of the most common diseases of the blood, anemia, can present with erythrocytes of normal size and color.

Normocytic-normochromic anemia is understood as the decrease in the total number of red blood cells, without alteration in their size or color. This means that its morphological development is apparently preserved as well as the amount of hemoglobin inside. The best known causes of this type of anemia include:

Bone marrow diseases

Aplastic anemia is a rare and serious disease that occurs when the production of red blood cells by the bone marrow is low. It is called aplastic because the histological study of the bone marrow, it looks empty or with few cells inside. The few red blood cells that are produced do not show alteration in their size or color.

This disease is characterized by the presence of fatigue, paleness, atraumatic bleeding, bruising, dizziness, headache, and tachycardia. The causes are diverse, among which are:

- Radiation

- Poisonings

- Medicinal

- Autoimmune diseases

- Viral infections

- Pregnancy

- Idiopathic

Renal insufficiency

When there is kidney failure there is also a shortage of erythropoietin. This hormone stimulates the bone marrow to produce erythrocytes, so if it is not present, the number of red blood cells that are formed will be less than usual. This phenomenon occurs regardless of the cause of kidney failure.

The few red blood cells that are produced are normocytic and normochromic. It has also been reported that erythrocytes produced in patients with renal failure live shorter lives.

The pathophysiological process of this fact is not known with certainty. These patients tend to have more frequent gastrointestinal bleeding.

Massive hemorrhages

Heavy bleeding causes normocytic and normochromic anemia. It occurs because the bone marrow does not have the ability to produce the same amount of erythrocytes that have been lost, decreasing their number globally. In these cases there is elevation of the reticulocytes.

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Hemolysis

It is a very similar condition to the previous one, but instead of hemorrhage there is massive destruction of erythrocytes. This reaction is usually caused by autoimmune diseases or certain poisonings.

The marrow is not capable of replacing the erythrocyte mass, but there is no deficit of elements necessary for the production of red blood cells.

Other causes

Several chronic diseases can cause normocytic and normochromic anemia. Among these we have:

- Chronic liver failure

- Infections (tuberculosis, pyelonephritis, osteomyelitis, endocarditis)

- Oncological diseases (adenocarcinomas, lymphomas)

- Myelodysplastic syndromes

- Endocrinopathies

- Rheumatological diseases (arthritis, polymalgia, panarteritis nodosa)

References

1. Torrens, Monica (2015). Clinical interpretation of the hemogram. Las Condes Clinical Medical Journal, 26 (6): 713-725.
2. Chiappe, Gustavo and collaborators (2012). Anemias Argentine Society of Hematology. Recovered from: sah.org.ar
3. Mayo Clinic (2016). Aplastic anemia. Recovered from: mayoclinic.org
4. National kidney Foundation (2006). Anemia and chronic kidney failure. Recovered from: kidney.org
5. Solís Jiménez, Joaquín and Montes Lluch, Manuel (2005). Anemias Geriatrics for Residents Treatise, Chapter 64, 55-665.
6. Wikipedia (2018). Red Blood Cell. Recovered from: en.wikipedia.org