From the Guidelines
Iron deficiency is associated with microcytic anemia because it impairs hemoglobin synthesis, leading to smaller red blood cells. When iron stores are depleted, the body cannot produce adequate hemoglobin, which is essential for oxygen transport 1. Hemoglobin consists of heme (containing iron) and globin protein chains. Without sufficient iron, heme production decreases, resulting in reduced hemoglobin content in developing red blood cells. These cells continue to divide but contain less hemoglobin, producing smaller (microcytic) cells with reduced mean corpuscular volume (MCV < 80 fL).
The process of iron deficiency leading to microcytic anemia can be understood by considering the stages of iron deficiency, ranging from iron depletion to iron-deficiency anemia 1. In iron-deficient erythropoiesis, stored iron is depleted and transport iron is reduced further, limiting red blood cell production and resulting in increased erythrocyte protoporphyrin concentration. In iron-deficiency anemia, the most severe form of iron deficiency, the shortage of iron leads to underproduction of iron-containing functional compounds, including hemoglobin, resulting in microcytic and hypochromic red blood cells 1.
Key characteristics of iron deficiency anemia include low ferritin, low serum iron, high total iron binding capacity, and low transferrin saturation 1. Treatment requires iron supplementation to replenish iron stores and correct the microcytosis. According to recent guidelines, iron replacement therapy (IRT) using the oral or intravenous route is effective in managing iron deficiency anemia 1. The most effective treatment approach involves iron supplementation, typically 325 mg of ferrous sulfate three times daily for 3-6 months, in combination with investigation to establish the underlying cause of iron deficiency 1.
From the Research
Definition and Causes of Microcytic Anemia
- Microcytic anemia is defined as anemia with a mean corpuscular volume (MCV) of less than 80 mcm3 in adults 2
- The most common cause of microcytic anemia is iron deficiency anemia, which can be managed with oral or intravenous iron, depending on the severity and comorbid conditions of the affected individual 3, 2
- Iron deficiency anemia occurs when the body's iron stores are depleted, often due to blood loss, impaired nutrition, or increased needs during pregnancy 4
Diagnosis and Differentiation of Microcytic Anemia
- Low serum ferritin is the best single laboratory parameter for the diagnosis of iron deficiency 5
- Serum iron, total iron binding capacity, and hemoglobin electrophoresis can help differentiate the type of microcytic anemia in patients with normal or elevated levels of serum ferritin 5
- The absence of iron stores in the bone marrow remains the most definitive test for differentiating iron deficiency from other microcytic states, such as anemia of chronic disease, thalassemia, and sideroblastic anemia 3
Association between Iron Deficiency and Microcytic Anemia
- Iron deficiency is the most common cause of microcytic anemia, and the two conditions are closely associated 3, 6, 2
- The human body maintains iron homeostasis by recycling the majority of its stores, but disruptions in this balance can lead to iron deficiency and microcytic anemia 3
- Blood loss is the most common cause of acute iron depletion and anemia worldwide, and reduced hemoglobin synthesis and anemia are the most common consequences of low plasma iron concentrations 4