Macrocytosis - Causes, Pathology, Diagnosis and Treatment

What Is Macrocytosis?

Macrocytosis is a blood-related condition also known as megalocytosis and macrocythemia. In macrocytosis, the red blood cells are larger in size than normal red blood cells; it can be calculated by evaluating the complete blood count showing the content of red blood cell size called – mean corpuscular volume (MCV). Because of the elevation in the mean corpuscular volume, the hemoglobin concentration is also elevated, as – mean corpuscular hemoglobin (MCH). Therefore, the peak in the values of mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) can indicate severe disorders like macrocytic anemia.

What Are the Causes of Macrocytosis?

• Macrocytosis can be caused by some developmental changes in the red blood cells or underlying disorders.

• The deficiency of vitamin B12 leads to the abnormal development of the red blood cells, which affects their functioning, the composition of the membrane of the red blood cells, and size. Vitamin B12 deficiency is seen when there is malabsorption of the vitamin in the small intestine or by prolonged inadequate intake of vitamin B12.

• The deficiency of folic acid can cause macrocytosis. Improper diet, alcoholism in females during pregnancy, malabsorption due to bowel syndrome, and liver disorders are the reasons for folate deficiency.

• Macrocytosis can also occur in conditions such as HIV (human immunodeficiency virus), Down’s syndrome (a person with an extra chromosome which may affect the growth), myelodysplastic syndrome (a type of malignancy caused by the immature blood cells found in bone marrow), multiple myeloma (cancer that forms in a type of white blood cell called a plasma cell), and hypothyroidism (thyroid gland fails to produce enough hormones). It can also be related to administered medications like Valproic Acid, Hydroxyurea, Allopurinol, Lamivudine, and Zidovudine.

• Macrocytosis is also seen as false elevation because of mishandling of the blood samples causing clumping of the blood.

What Are the Clinical Features of Macrocytosis?

The clinical features of macrocytosis are as follows -

1. Males are more likely to get affected.

2. 40 percent to 45 percent of patients are associated with anemia.

3. Fatigue.

4. Diarrhea.

5. Tachycardia (increase in heart rate).

6. Shortness of breath.

7. Inflammation of the tongue.

8. Pale skin

9. Memory loss.

10. Loss of weight.

What Is the Pathophysiology of Macrocytosis?

Macrocytosis can be classified into two types depending upon pathophysiology -

Megaloblastic Macrocytosis -

Megaloblastic macrocytosis occurs due to the abnormal production of red blood cells and has macroovalocytes and segmented neutrophils seen in peripheral smears. In megaloblastic, the precursor of red blood cells are larger than the mature ones due to the deficiency of vitamin B12 and folate leads to the defective production of RNA (ribonucleic acid) and DNA (deoxyribonucleic acid). It is caused due to -

1. Vitamin B12 deficiency.

2. Folate deficiency.

3. Inherited disorders.

4. Medications that are used to treat HIV (Human Immunodeficiency Virus), chemotherapy, and antiseizure.

Non-Megaloblastic Macrocytosis -

Non-megaloblastic macrocytosis occurs due to some inducing factors; it has macroreticulocytes seen in the reticulocyte count. Therefore, it is done to differentiate macrocytosis from megaloblastic and non-megaloblastic. In non-megaloblastic, there is excessive production of red blood cells to compensate for the blood loss or hemolysis of the red blood cells, causing reticulocytosis. Reticulocytes are abnormal red blood cells does not get mature; therefore, they are large in size. The factors involved are -

1. Alcoholism.

2. Hypothyroidism.

3. Liver disorders.

4. Hemolysis.

5. Hemorrhage.

6. Myelodysplasia.

7. Chronic obstructive pulmonary disorder.

8. Splenomegaly.

What Are the Normal Ranges of Mean Corpuscular Volume (MCV) And Mean Corpuscular Hemoglobin (MCH)?

The mean corpuscular volume (MCV) is the average size of red blood cells and is expressed in cubic microns (cu) or femtoliters (fl). When the mean corpuscular volume is normal, the red blood cells are called —normocyte; when the volume increases, the red blood cells are called —macrocytes, and if the volume is decreased, the red blood cells are known as —microcytes.

The normal range of mean corpuscular volume is 78 to 90 cu.

The mean corpuscular hemoglobin (MCH) is the average amount of hemoglobin content present in the red blood cells. It is evaluated in micro-microgram and picograms (pg).

The normal range of the mean corpuscular volume is 27 to 32 pg.

What Are the Investigations for the Diagnosis of Macrocytosis?

Macrocytosis can be diagnosed by examining the patient physically and recording their medical and personal history. It is also essential to understand any underlying disease due to which there is an elevation in the range of mean corpuscular volume (MCV).

According to the patient's symptoms, the advised investigations are as follows -

1. Complete Blood Count (CBC) - Complete blood count (CBC) is done to know the average range of mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH).

2. Complete Blood Picture (CBP) - Complete blood picture is done to check the deficiencies of vitamin B12 and folate because these deficiencies can lead to anemia and abnormal production of red blood cells.

3. Peripheral Blood Smear - Peripheral blood smear is done to see the megaloblastic changes in the blood.

4. Reticulocyte Count - Reticulocyte count is done to differentiate between megaloblastic, macrocytosis, and non-macrocytosis.

Other investigations can also be performed for confirmation like — renal function test, thyroid-stimulating hormone test (TSH), iron absorption test, and biopsy of bone marrow to check the aplasia, dysplasia, or malignancy, and urine analysis is also done.

What Are the Treatment Modalities for Macrocytosis?

The treatment for macrocytosis is done according to the etiology, investigational findings, and other related disorders. If vitamin B12 and folate are deficient, it is advised to have supplements of vitamin B12 and folate. Because of some gastrointestinal problems, it is better to see a gastroenterologist for malabsorption.

Macrocytosis due the alcoholism can lead to multiple organ failures; therefore, alcohol cessation is advised. Refer to their specialist for underlying diseases like thyroid, bone marrow disease, and malignancy.

How to Prevent Macrocytosis?

Prevention of macrocytosis can be done by having a balanced diet. A balanced diet provides all the supplements required for the body to function at its best potential. Regular health checkups should be done to find any underlying causes. Early detection helps in the treatment without letting the condition get worse.

Conclusion -

Macrocytosis refers to the larger red blood cells in the bloodstream, it does not have any particular symptoms, but it may be associated with some other diseases. Macrocytic anemia is mainly associated with it. The deficiency of vitamin B12 and folate can impair the production of red blood cells leading to large immature red blood cells. Leading a healthy and physically fit life can help to regulate and metabolize all the nutritional supplements for the body to work in harmony.