ALL YOU NEED TO KNOW ABOUT ANEMIAS

Introduction

Anemia is a medical condition in which a person has a lower-than-normal number of red blood cells (RBCs) or hemoglobin, the protein in red blood cells that carries oxygen to the body’s tissues. This results in reduced oxygen delivery to the body’s organs and tissues, leading to fatigue, weakness, and other symptoms.

Anemia can be caused by a variety of factors, including iron deficiency, vitamin deficiency, chronic diseases, blood loss, and genetic disorders. The most common type of anemia is iron-deficiency anemia, which occurs when the body does not have enough iron to produce hemoglobin. Other types of anemia include pernicious anemia, sickle cell anemia, and aplastic anemia.

Symptoms of anemia can include fatigue, weakness, shortness of breath, dizziness, headache, pale skin, and rapid heartbeat. Treatment for anemia depends on the underlying cause but may involve iron supplements, vitamin supplements, blood transfusions, or medication.

 

The maturational sequence of erythroid cells in the bone marrow consists of several stages, each characterized by distinct morphological and functional features. The sequence starts with the formation of a proerythroblast, which is a large nucleated cell with a high nuclear-cytoplasmic ratio. The proerythroblast then undergoes several rounds of cell division, resulting in the formation of smaller cells called erythroblasts. Erythroblasts are still nucleated but have a lower nuclear-cytoplasmic ratio and have begun to produce hemoglobin.

As the erythroblast continues to mature, it becomes a normoblast, which is a smaller cell with a condensed nucleus and more hemoglobin. At this stage, the normoblast is still capable of cell division, but it soon loses its nucleus and becomes a reticulocyte. Reticulocytes are immature red blood cells that still contain remnants of ribosomal RNA, giving them a reticular or net-like appearance under a microscope.

Finally, the reticulocyte is released into the circulation, where it completes its maturation by losing its ribosomal RNA and becoming a fully mature erythrocyte, or red blood cell. The entire process of erythropoiesis takes about 7-10 days in humans and is tightly regulated by the hormone erythropoietin, which is produced by the kidneys in response to low oxygen levels.

 

Aplastic anemia is a rare but serious hematologic disorder characterized by a decrease in the number of blood cells due to failure of the bone marrow to produce them. In this condition, the bone marrow does not produce enough red blood cells, white blood cells, and platelets, leading to anemia, increased susceptibility to infections, and bleeding.

Etiology: The cause of aplastic anemia is not well understood. However, it can be associated with several factors, including exposure to certain drugs, chemicals, and radiation, viral infections such as hepatitis, parvovirus B19, and HIV, genetic predisposition, autoimmune disorders, and idiopathic causes.

Diagnostic criteria: The diagnosis of aplastic anemia is made based on clinical features, blood counts, bone marrow biopsy, and genetic testing. The diagnostic criteria for aplastic anemia include a peripheral blood count showing pancytopenia (low red blood cells, white blood cells, and platelets), a bone marrow biopsy showing a hypocellular bone marrow with less than 30% cellularity, and the absence of any other underlying causes for pancytopenia.

Clinical features: The clinical features of aplastic anemia include fatigue, weakness, shortness of breath, palpitations, frequent infections, bleeding from the gums and nose, petechiae, ecchymoses, and prolonged bleeding after minor injuries. The severity of the symptoms varies from patient to patient and depends on the extent of the bone marrow failure.

Management: The management of aplastic anemia involves a multidisciplinary approach, including supportive care, immunosuppressive therapy, and stem cell transplantation. The supportive care includes blood transfusions, antibiotics for infections, and platelet transfusions for bleeding. Immunosuppressive therapy involves the use of drugs such as antithymocyte globulin (ATG) and cyclosporine to suppress the immune system and stimulate the bone marrow to produce more blood cells. Stem cell transplantation is considered in young patients who have a matched donor and have failed immunosuppressive therapy.

In conclusion, aplastic anemia is a rare but serious hematologic disorder that requires prompt diagnosis and management. Early detection and treatment can improve the prognosis and prevent complications associated with bone marrow failure.

 

Myelophthisic anemias are a group of rare disorders characterized by the replacement of normal bone marrow cells with abnormal or infiltrating cells, leading to anemia and other symptoms. The classification of myelophthisic anemias is based on the underlying cause of bone marrow infiltration, and the most common causes include:

1. Metastatic cancer: Cancer cells from other parts of the body can spread to the bone marrow and replace the normal cells. Common types of cancer that can cause myelophthisic anemia include breast, lung, and prostate cancer.
2. Hematologic malignancies: Certain types of blood cancers, such as leukemia, lymphoma, and multiple myeloma, can also infiltrate the bone marrow and cause myelophthisic anemia.
3. Infections: Rarely, severe infections such as tuberculosis or histoplasmosis can cause myelophthisic anemia by directly infiltrating the bone marrow.
4. Inflammatory disorders: Some chronic inflammatory disorders, such as sarcoidosis, can also cause bone marrow infiltration and myelophthisic anemia.

Overall, the treatment of myelophthisic anemias is focused on addressing the underlying cause of bone marrow infiltration and may include chemotherapy, radiation therapy, or other targeted therapies depending on the specific cause.

 

Erythropoietin in hematopoiesis

Erythropoietin (EPO) is a glycoprotein hormone that plays a critical role in hematopoiesis, the process of blood cell formation. It is primarily produced in the kidneys in response to low oxygen levels, although a smaller amount is also produced in the liver.

EPO acts on the bone marrow, where it stimulates the production of red blood cells (erythrocytes) from progenitor cells called erythroid precursors. These precursors differentiate into mature erythrocytes that are released into the bloodstream. EPO also enhances the survival and proliferation of erythroid precursors, leading to an increased production of erythrocytes.

In addition to its role in erythropoiesis, EPO also has other functions. It can promote the differentiation of megakaryocytes, which are the precursors of platelets, and it has been shown to have neuroprotective effects.

The target cells of EPO are erythroid precursors, which are found in the bone marrow. EPO binds to its receptor on the surface of these cells, activating a signaling pathway that leads to increased survival, proliferation, and differentiation of the precursors into erythrocytes.

In summary, EPO plays a critical role in hematopoiesis by stimulating the production of erythrocytes from erythroid precursors in the bone marrow. Its site of production is primarily in the kidneys, and its target cells are erythroid precursors in the bone marrow.

 

Anemias according to mean corpuscular volume

Anemias can be classified based on their mean corpuscular volume (MCV), which is the average volume of red blood cells in a given sample. The MCV can be used to differentiate between different types of anemia. The three main classifications of anemia based on MCV are:

1) Microcytic anemia: In microcytic anemia, the MCV is less than 80 femtoliters (fl). This is usually due to a decrease in hemoglobin synthesis, resulting in smaller and paler red blood cells. Examples of microcytic anemias include:

• Iron deficiency anemia
• Thalassemia
• Anemia of chronic disease

 

2) Normocytic anemia: In normocytic anemia, the MCV is within the normal range of 80-100 fl. This type of anemia is usually due to a decrease in the number of red blood cells or hemoglobin. Examples of normocytic anemias include:

• Anemia of chronic kidney disease
• Aplastic anemia
• Hemolytic anemia

 

3) Macrocytic anemia: In macrocytic anemia, the MCV is greater than 100 fl. This is usually due to a deficiency in vitamin B12 or folic acid, leading to larger and immature red blood cells. Examples of macrocytic anemias include:

• Vitamin B12 deficiency anemia
• Folic acid deficiency anemia
• Myelodysplastic syndrome

 

It is important to note that the classification of anemia based on MCV alone may not always be sufficient, and further tests may be required to determine the underlying cause of the anemia.

 

Anemias according to pathophysiologic criteria

Anemia is a condition characterized by a decrease in the number of red blood cells or a decrease in the amount of hemoglobin in the blood. It can be classified according to several pathophysiologic criteria, including:

1) Production Defect Anemias: These anemias are caused by a defect in the production of red blood cells. They can be further classified into:

• Iron-deficiency anemia: This is the most common type of anemia, caused by a deficiency of iron which is necessary for the production of hemoglobin.
• Vitamin-deficiency anemia: This type of anemia is caused by a deficiency of vitamins like vitamin B12 or folic acid, which are essential for the production of red blood cells.
• Aplastic anemia: This is a rare type of anemia caused by a failure of the bone marrow to produce red blood cells.

 

2) Hemolytic Anemias: These anemias are caused by the premature destruction of red blood cells. They can be further classified into:

• Immune hemolytic anemia: This type of anemia is caused by the immune system attacking and destroying red blood cells.
• Non-immune hemolytic anemia: This type of anemia is caused by factors outside the immune system, such as toxins or infections.

 

3) Blood Loss Anemias: These anemias are caused by blood loss from the body. They can be further classified into:

• Acute blood loss anemia: This type of anemia is caused by sudden and severe blood loss, such as from a trauma or surgery.
• Chronic blood loss anemia: This type of anemia is caused by ongoing and long-term blood loss, such as from gastrointestinal bleeding.

 

 

The reticulocyte count is a laboratory test that measures the percentage of immature red blood cells (reticulocytes) in the bloodstream. Reticulocytes are produced by the bone marrow in response to low levels of red blood cells (anemia) or in situations of increased demand for oxygen-carrying capacity, such as during high-altitude exposure or intense physical activity.

A normal reticulocyte count ranges from 0.5 to 2.5% of total red blood cells, depending on the laboratory reference range. However, the absolute reticulocyte count may vary based on the patient’s age, gender, and medical condition.

The corrected reticulocyte count is a calculation that adjusts the reticulocyte count based on the degree of anemia present. The corrected reticulocyte count formula is as follows:

Corrected reticulocyte count = reticulocyte count x (patient’s hematocrit/normal hematocrit)

A corrected reticulocyte count greater than 3% indicates an appropriate bone marrow response to anemia, while a value below 2% suggests decreased erythropoietic activity or bone marrow suppression.

Diseases associated with high reticulocyte counts include hemolytic anemia, which is characterized by the premature destruction of red blood cells, leading to an increased demand for reticulocyte production. Other conditions that can cause high reticulocyte counts include acute blood loss, hemolytic transfusion reactions, and erythroblastosis fetalis.

Diseases associated with low reticulocyte counts include aplastic anemia, which is characterized by bone marrow failure and a reduced production of all blood cell types, including reticulocytes. Other conditions that can cause low reticulocyte counts include iron deficiency anemia, myelodysplastic syndrome, and chemotherapy-induced bone marrow suppression.