Microcytic anemia


Microcytic anaemia is any of several types of anaemia characterized by small red blood cells. The normal mean corpuscular volume is approximately 80–100 fL. When the MCV is <80 fL, the red cells are described as microcytic and when >100 fL, macrocytic. The MCV is the average red blood cell size.
In microcytic anaemia, the red blood cells contain less hemoglobin and are usually also hypochromic, meaning that the red blood cells appear paler than usual. This can be reflected by a low mean corpuscular hemoglobin concentration, a measure representing the amount of hemoglobin per unit volume of fluid inside the cell; normally about 320–360 g/L or 32–36 g/dL. Typically, therefore, anemia of this category is described as "microcytic, hypochromic anaemia".

Causes

Typical causes of microcytic anemia include:
Other causes that are typically thought of as causing normocytic anemia or macrocytic anemia must also be considered, and the presence of two or more causes of anemia can distort the typical picture.
There are five main causes of microcytic anemia forming the acronym TAILS. Thalassemia, anemia of chronic disease, iron deficiency, lead poisoning and congenital sideroblastic anemia. Only the first three are common in most parts of the world. In theory, these three can be differentiated by their red blood cell morphologies. Anemia of chronic disease shows unremarkable RBCs, iron deficiency shows anisocytosis, anisochromia and elliptocytosis, and thalassemias demonstrate target cells and coarse basophilic stippling. In practice though elliptocytes and anisocytosis are often seen in thalassemia and target cells occasionally in iron deficiency. All three may show unremarkable RBC morphology. Basophilic stippling is one morphologic finding of thalassemia which does not appear in iron deficiency or anemia of chronic disease. The patient should be in an ethnically at risk group and the diagnosis is not confirmed without a confirmatory method such as hemoglobin HPLC, H body staining, molecular testing or another reliable method. Coarse basophilic stippling occurs in other cases as seen in Table 1.