Microcytic anaemia is any of several types of anemia characterized by smaller than normal red blood cells (called microcytes). The normal mean corpuscular volume of a red blood cell is approximately 80–100 fL. When the MCV is <80 fL, the red cells are described as microcytic. MCV is the average red blood cell size. The main causes of microcytic anemia are iron-deficiency, lead poisoning, thalassemia, and anemia of chronic disease.

In microcytic anemia, the red blood cells (erythrocytes) 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 (MCHC), 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 anemia".

Causes

Typical causes of microcytic anemia include:

  • Childhood
  • Iron deficiency anemia (50% of all anemias in humans are due to iron-deficiency)
  • Thalassemia
  • Adulthood
  • Iron deficiency anemia
  • Thalassemia
  • Anemia of chronic disease

Rare hereditary causes of microcytic anemia include sideroblastic anemia and other X-linked anemias, hereditary hypotransferrinemia, hereditary aceruloplasminemia, erythropoietic protoporphyria, iron-refractory iron deficiency anemia, and other thalassemic mutations (such as hemoglobin E and hemoglobin Lepore syndrome).

Rarer acquired causes of microcytic anemia include lead poisoning, zinc deficiency, copper deficiency, alcohol, and certain medications. Although it is a common nutritional disorder, most causes of iron-deficiency anemia (IDA) are due to blood loss. A patient may present with pallor, conjunctivitis, tachycardia, increased respiratory rate, exhaustion, or koilonychia (spoon-shaped nails); severe cases may also present with angina.

Anemia of chronic disease

Anemia of chronic disease (ACD) is the second most common cause of anemia after IDA.

Anemia of chronic disease is usually a result of chronic infections, autoimmune diseases, and cancer. It also occurs in individuals that have chronic inflammation due to a medical condition. Diagnosis may involve a review of the morphology of the blood film and bone marrow, reticulocyte count, stool analysis, serum bilirubin and lactate dehydrogenase assay, and assessment of renal function. Folic acid supplements are also recommended for some cases of thalassemia.

As IDA and ACD can often be confused, it is important to evaluate their laboratory parameters. IDA is associated with low hemoglobin, ferritin, transferrin saturation, and MCV. In the latter case, the anemia can be treated via either dietary or pharmacological (oral or intravenous) iron supplementation. Blood transfusions may be necessary for more severe cases; to prevent iron overload due to transfusions, chelation therapy may also be required to remove excess iron from the body.

Outlook

The prognosis for microcytic anemias depends on the cause of the anemia and the speed with which it is treated. For IDA, the prognosis is excellent as long as the underlying cause of the deficiency is addressed.

See also

  • Hypochromic anemia

References

  • Emedicine on chronic anemia