Microcytic Anaemia
Microcytosis is the presence of red cells that are smaller than normal. Normal adult red cell has a diameter of 7.2 µm. Microcytes are commonly seen with hypochromia in iron-deficiency anaemia, thalassaemia trait, congenital sideroblastic anaemia, and sometimes in anaemia of chronic diseases.
Introduction
Microcytic anaemia is characterised by red blood cells (RBCs) that are smaller than normal, with a mean corpuscular volume (MCV) of less than 80 fL. This condition often presents with hypochromia, where the RBCs appear paler than usual due to lower haemoglobin content. Common causes include iron deficiency anaemia (IDA), thalassaemia, and anaemia of chronic disease (ACD).
Causes
Iron-Deficiency Anaemia
Iron deficiency anaemia is the most prevalent cause of microcytic anaemia and is often due to blood loss rather than inadequate dietary intake. It is common in children and menstruating females. Diagnostic criteria include low MCV, serum ferritin levels, and transferrin saturation. Differential diagnoses include lead poisoning, haemoglobinopathies, and other conditions causing fatigue.
Anaemia of Chronic Disease
ACD is the second most common cause of anaemia and is associated with chronic inflammation due to conditions like rheumatoid arthritis, malignancies, and tuberculosis. Diagnosis involves exclusion and may include blood film morphology, reticulocyte count, and serum markers. Treatment focuses on the underlying inflammatory condition rather than the anaemia itself.
Thalassaemia
Thalassaemia is an inherited disorder affecting the globin genes, resulting in reduced haemoglobin production. It is classified into alpha and beta thalassaemia based on the affected globin chain. Diagnosis is made through DNA and haemoglobin analysis. Management includes chronic transfusions and folic acid supplements to mitigate symptoms and complications.
Signs and Symptoms
Patients with microcytic anaemia may present with pallor, conjunctivitis, tachycardia, increased respiratory rate, exhaustion, and in severe cases, angina. Specific conditions like IDA may also cause koilonychia (spoon-shaped nails), while ACD may be asymptomatic or present with mild symptoms like fatigue and headache.
Evaluation and Diagnosis
Differentiating between IDA, ACD, and thalassaemia can be challenging due to overlapping RBC morphologies. IDA typically shows anisocytosis, anisochromia, and elliptocytosis, whereas thalassaemia may present with target cells and basophilic stippling. Laboratory parameters help differentiate these conditions: IDA is associated with low haemoglobin, ferritin, transferrin saturation, and MCV, whereas ACD may show normal-high ferritin and high C-reactive protein levels.
Treatment
Iron-Deficiency Anaemia
Treatment involves addressing the underlying cause and iron supplementation. Dietary iron intake, especially from heme sources like liver and red meats, can help, but pharmacological agents (oral or intravenous iron) are often required for severe deficiencies. Oral iron supplements should be taken on an empty stomach to enhance absorption, though this may increase side effects.
Anaemia of Chronic Disease
Iron therapy may be ineffective for ACD due to the relative deficiency of available iron. Treatments include red cell transfusion, ω-3 poly-unsaturated fatty acids, or erythropoiesis-stimulating agents. Managing the underlying inflammatory disorder is very important.
Thalassaemia
Mild thalassaemia cases may require folic acid supplements, while severe cases need regular blood transfusions and chelation therapy to prevent iron overload. Advanced treatments include bone marrow transplant, haematopoietic stem cell transplantation, and gene therapy.
Prognosis
The outlook for microcytic anaemias varies. IDA has an excellent prognosis if the cause is addressed, but untreated deficiency can lead to severe complications like cognitive impairment and heart conditions. The prognosis for ACD depends on the underlying cause, while thalassaemia outcomes vary based on severity and treatment consistency.
Self-assessment MCQs (single best answer)
What is the mean corpuscular volume (MCV) threshold for microcytic anaemia?
Which of the following is the most common cause of microcytic anaemia?
What condition is characterised by red blood cells appearing paler than usual due to lower haemoglobin content?
Which of the following is a common symptom of microcytic anaemia?
In iron-deficiency anaemia, which laboratory finding is typically low?
What type of cells might you expect to see on a blood film in a patient with thalassaemia?
Which of the following conditions is associated with chronic inflammation and can lead to anaemia of chronic disease (ACD)?
What is a potential severe complication of untreated iron-deficiency anaemia?
What is the primary treatment for iron-deficiency anaemia?
What advanced treatment option is available for severe cases of thalassaemia?
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