Anaemia

Anaemia is a condition characterized by a deficiency in the number or quality of red blood cells (RBCs) or haemoglobin, leading to a reduced capacity of the blood to carry oxygen. It can result in symptoms like fatigue, weakness, pallor, and shortness of breath.

Definition of Anaemia

Anaemia is a reduction in the quantity or functionality of red blood cells (RBCs) or haemoglobin in the blood. Haemoglobin is the protein in RBCs responsible for oxygen transport. When haemoglobin levels drop below normal ranges, the body’s ability to deliver oxygen to tissues and organs is compromised, leading to fatigue, weakness, and pallor.

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Classification of Anaemia

Anaemia can be classified in several ways:

Based on Cause

1. Nutritional Deficiencies

• Iron-deficiency Anaemia

Causes:

• • Inadequate dietary intake of iron.
  • Poor absorption (e.g., celiac disease, gastric bypass surgery).
  • Chronic blood loss (e.g., heavy menstruation, gastrointestinal bleeding).

Mechanism: Insufficient iron decreases haemoglobin synthesis, resulting in smaller (microcytic) and paler (hypochromic) red blood cells.

• Vitamin B12 Deficiency Anaemia

Causes:

• • Dietary deficiency (common in strict vegetarians).
  • Malabsorption (e.g., pernicious anaemia due to lack of intrinsic factor, gastrointestinal disorders).
  • Increased demand (e.g., during pregnancy).

Mechanism: Impaired DNA synthesis leads to ineffective erythropoiesis and the production of larger (macrocytic) red blood cells.

• Folate Deficiency Anaemia

Causes:

• • Inadequate dietary intake (especially in pregnant women).
  • Malabsorption syndromes (e.g., celiac disease).
  • Increased demand (e.g., during pregnancy or rapid cell turnover).

Mechanism: Like vitamin B12, folate deficiency leads to defective DNA synthesis and macrocytic red blood cells.

2. Chronic Diseases

• Anaemia of Chronic Disease (ACD)

Causes:

• • Chronic infections (e.g., tuberculosis).
  • Inflammatory diseases (e.g., rheumatoid arthritis, lupus).
  • Malignancies (e.g., cancer).

Mechanism: Inflammatory cytokines lead to iron sequestration and reduced erythropoietin production, resulting in normocytic red blood cells that are often less responsive to erythropoiesis.

3. Bone Marrow Disorders

   • Aplastic Anaemia

Causes:

• • Autoimmune disorders (where the immune system attacks bone marrow).
  • Exposure to toxins (e.g., benzene, certain medications).
  • Viral infections (e.g., hepatitis, Epstein-Barr virus).

Mechanism: Failure of the bone marrow to produce sufficient red blood cells, leading to a decrease in all blood cell types (pancytopenia).

• Myelodysplastic Syndromes (MDS)

Causes:

• • Genetic mutations are often associated with age.
  • Exposure to chemotherapy or radiation.

Mechanism: Ineffective haematopoiesis leads to dysplastic (abnormal) cells and low red blood cell counts.

• Leukaemia

Causes:

• • Various factors, including genetic predispositions and environmental exposures.

Mechanism: Malignant proliferation of immature white blood cells crowds out normal haematopoiesis, leading to anaemia.

4. Haemolytic Anaemias

• Autoimmune Haemolytic Anaemia

Causes:

• • Autoimmune disorders (e.g., lupus).
  • Certain infections or medications.

Mechanism: The immune system mistakenly attacks and destroys red blood cells, leading to increased RBC destruction and often resulting in jaundice.

• Sickle Cell Anaemia

Causes:

• • Genetic mutation in the haemoglobin gene (autosomal recessive inheritance).

Mechanism: Abnormal haemoglobin (haemoglobin S) causes red blood cells to assume a sickle shape, leading to blockages in blood flow and increased haemolysis.

• Thalassemia

Causes:

• • Genetic mutations affecting globin chain production (alpha or beta thalassemia).

Mechanism: Ineffective erythropoiesis and haemolysis of abnormal red blood cells, leading to microcytic anaemia.

5. Blood Loss

• Acute Blood Loss

Causes:

• • Trauma, surgery, or significant haemorrhage.

Mechanism: Rapid blood loss leads to a sudden drop in red blood cell count, often presenting as normocytic anaemia initially.

• Chronic Blood Loss

Causes:

• • Gastrointestinal bleeding (ulcers, cancers).
  • Heavy menstrual periods (menorrhagia).

Mechanism: Ongoing loss of red blood cells can lead to iron-deficiency anaemia over time as iron stores are depleted.

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Based on Morphology

1. Microcytic Anaemia

Definition: Microcytic anaemia is characterized by smaller-than-normal red blood cells, typically indicated by a low mean corpuscular volume (MCV < 80 fL).

Causes:

• Iron deficiency anaemia: The most common cause resulting from insufficient iron for haemoglobin synthesis. This can stem from dietary deficiency, malabsorption, or chronic blood loss.
• Thalassemia: A genetic disorder affecting haemoglobin production, reducing RBC production and smaller cells.
• Anaemia of Chronic Disease: Inflammation can cause iron sequestration, leading to inadequate iron availability for haemoglobin synthesis.
• Sideroblastic anaemia: A rare disorder where the bone marrow produces ringed sideroblasts instead of normal RBCs due to issues with iron metabolism.

Morphological Features:

• Smaller RBCs
• Often hypochromic (paler than normal due to low haemoglobin content)
• Variations in RBC size (anisocytosis) and shape (poikilocytosis) may be present.

Symptoms:

Fatigue, weakness, pallor, and sometimes signs of iron deficiency like brittle nails or angular cheilitis.

2. Macrocytic Anaemia

Definition: Macrocytic anaemia is characterized by larger-than-normal red blood cells, indicated by a high mean corpuscular volume (MCV > 100 fL).

Causes:

• Vitamin B12 Deficiency Can arise from dietary lack, pernicious anaemia (lack of intrinsic factor), or malabsorption (e.g., in Crohn’s disease).
• Folate Deficiency: Often due to inadequate dietary intake, malabsorption, or increased demand (e.g., during pregnancy).
• Myelodysplastic Syndromes: A group of disorders caused by poorly formed or dysfunctional blood cells due to ineffective haematopoiesis.
• Liver Disease: This can lead to altered lipid metabolism, resulting in abnormally sized RBCs.

Morphological Features:

• Larger RBCs
• Hyperchromic (darker than normal due to increased haemoglobin content)
• Presence of oval macrocytes and possibly hyper-segmented neutrophils (particularly in vitamin B12 deficiency).

Symptoms:

Fatigue, weakness, pallor, neurological symptoms (in vitamin B12 deficiency), and glossitis.

3. Normocytic Anaemia

Definition: Normocytic anaemia is characterized by red blood cells of normal size (normal MCV, typically between 80-100 fL) but is present in reduced numbers.

Causes:

• Anaemia of Chronic Disease: Commonly seen in chronic infections, inflammatory diseases, and malignancies. The inflammation leads to reduced erythropoiesis and iron sequestration.
• Acute Blood Loss: Following trauma or surgery can temporarily drop RBC count without altering cell size.
• Renal Failure: Reduced erythropoietin (EPO) production stimulates RBC production.
• Aplastic anaemia: A condition where the bone marrow fails to produce adequate blood cells, affecting all cell lines.

Morphological Features:

• Normal-sized RBCs
• Typically, normal haemoglobin content
• May show decreased reticulocyte counts (low production of new RBCs).

Symptoms:

Fatigue, weakness, pallor, and symptoms related to the underlying cause (e.g., infection or chronic disease).

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Based on Severity

1. Mild Anaemia

• Haemoglobin Levels:
  • Typically, between 10-11 g/dL (for adult women) and 10-12 g/dL (for adult men).
• Symptoms:
  • Often asymptomatic or may present with mild fatigue and weakness.
  • Symptoms may be non-specific and can be mistaken for normal fatigue.
• Management:
  • It may involve dietary changes or supplementation (e.g., iron, B12) based on the underlying cause.
  • Regular monitoring is important to prevent progression.

2. Moderate Anaemia

• Hemoglobin Levels:
  • Ranges from 7 to 10 g/dL.
• Symptoms:
  • More pronounced fatigue, weakness, palpitations, and exertional dyspnea.
  • Possible pale skin and mucous membranes.
• Management:
  • Often requires treatment of the underlying cause.
  • It may involve iron or vitamin supplementation and lifestyle modifications.
  • Regular follow-up and monitoring are crucial.

3. Severe Anaemia

• Haemoglobin Levels:
  • Less than 7 g/dL.
• Symptoms:
  • Significant fatigue, marked pallor, tachycardia, and shortness of breath even at rest.
  • Risk of serious complications such as heart failure due to inadequate oxygen delivery to tissues.

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Diagnosis

Diagnosis involves a combination of clinical evaluation and laboratory tests, including:

• Complete Blood Count (CBC):

Measures haemoglobin levels, haematocrit, RBC count, and indices (MCV, MCH, MCHC) to determine the type of anaemia.

• Reticulocyte Count:

Assesses bone marrow response to anaemia by measuring immature RBCs.

• Iron Studies:

Includes serum iron, ferritin, total iron-binding capacity (TIBC), and transferrin saturation to evaluate iron deficiency.

• Vitamin B12 and Folate Levels:

To check for deficiencies.

• Bone Marrow Biopsy:

This may be performed in suspected aplastic anaemia or malignancy cases.

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Management

Treatment of anaemia depends on its underlying cause:

• Iron-deficiency Anaemia:

Oral or intravenous iron supplements, dietary modifications, and addressing the source of blood loss.

• Vitamin B12 and Folate Deficiencies:

Intramuscular vitamin B12 injections, oral folate supplements, and dietary advice.

• Anaemia of Chronic Disease:

Management focuses on treating the underlying disease, although erythropoiesis-stimulating agents may sometimes be used.

• Hemolytic Anaemias:

Treatment may involve corticosteroids, immunosuppressants, or splenectomy depending on the type.

• Aplastic Anaemia:

Treatment options include immunosuppressive therapy, bone marrow transplant, or supportive care with blood transfusions.

• Severe Anaemia:

Blood transfusions may be required for rapid correction, especially in emergencies.